Bump actions/cache from 1 to 2.1.6
diff --git a/.github/workflows/ci-testing.yml b/.github/workflows/ci-testing.yml
index 1b29173b83a..6d1603880f4 100644
--- a/.github/workflows/ci-testing.yml
+++ b/.github/workflows/ci-testing.yml
@@ -39,7 +39,7 @@ jobs:
           python -c "from pip._internal.locations import USER_CACHE_DIR; print('::set-output name=dir::' + USER_CACHE_DIR)"
 
       - name: Cache pip
-        uses: actions/cache@v1
+        uses: actions/cache@v2.1.6
         with:
           path: ${{ steps.pip-cache.outputs.dir }}
           key: ${{ runner.os }}-${{ matrix.python-version }}-pip-${{ hashFiles('requirements.txt') }}

Bumps [actions/cache](https://github.com/actions/cache) from 1 to 2.1.6.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/actions/cache/releases">actions/cache's releases</a>.</em></p>
<blockquote>
<h2>v2.1.6</h2>
<ul>
<li>Catch unhandled &quot;bad file descriptor&quot; errors that sometimes occurs when the cache server returns non-successful response (<a href="https://github-redirect.dependabot.com/actions/cache/pull/596">actions/cache#596</a>)</li>
</ul>
<h2>v2.1.5</h2>
<ul>
<li>Fix permissions error seen when extracting caches with GNU tar that were previously created using BSD tar (<a href="https://github-redirect.dependabot.com/actions/cache/issues/527">actions/cache#527</a>)</li>
</ul>
<h2>v2.1.4</h2>
<ul>
<li>Make caching more verbose <a href="https://github-redirect.dependabot.com/actions/toolkit/pull/650">#650</a></li>
<li>Use GNU tar on macOS if available <a href="https://github-redirect.dependabot.com/actions/toolkit/pull/701">#701</a></li>
</ul>
<h2>v2.1.3</h2>
<ul>
<li>Upgrades <code>@actions/core</code> to v1.2.6 for <a href="https://github.com/advisories/GHSA-mfwh-5m23-j46w">CVE-2020-15228</a>. This action was not using the affected methods.</li>
<li>Fix error handling in <code>uploadChunk</code> where 400-level errors were not being detected and handled correctly</li>
</ul>
<h2>v2.1.2</h2>
<ul>
<li>Adds input to limit the chunk upload size, useful for self-hosted runners with slower upload speeds</li>
<li>No-op when executing on GHES</li>
</ul>
<h2>v2.1.1</h2>
<ul>
<li>Update <code>@actions/cache</code> package to <code>v1.0.2</code> which allows cache action to use posix format when taring files.</li>
</ul>
<h2>v2.1.0</h2>
<ul>
<li>Replaces the <code>http-client</code> with the Azure Storage SDK for NodeJS when downloading cache content from Azure.  This should help improve download performance and reliability as the SDK downloads files in 4 MB chunks, which can be parallelized and retried independently</li>
<li>Display download progress and speed</li>
</ul>
<h2>v2.0.0</h2>
<p>Initial v2 release</p>
<h2>What's new in v2</h2>
<ul>
<li>Added support for multiple paths (<a href="https://github-redirect.dependabot.com/actions/cache/issues/16">actions/cache#16</a>), glob patterns, and single file caches (<a href="https://github-redirect.dependabot.com/actions/cache/issues/33">actions/cache#33</a>)</li>
<li>Increased performance and improved cache sizes using <code>zstd</code> for compression for Linux and macOS runners (<a href="https://github-redirect.dependabot.com/actions/cache/issues/184">actions/cache#184</a>)</li>
<li>Allowed caching for all events with a ref (<a href="https://github-redirect.dependabot.com/actions/cache/issues/63">actions/cache#63</a>)</li>
<li>Created the <a href="https://github.com/actions/toolkit/tree/master/packages/cache"><code>@actions/cache</code></a> npm package to allow other actions to utilize caching (<a href="https://github-redirect.dependabot.com/actions/cache/issues/55">actions/cache#55</a>)</li>
<li>Added a best-effort step to delete the archive after extraction to reduces storage space (<a href="https://github-redirect.dependabot.com/actions/cache/pull/209">actions/cache#209</a>)</li>
</ul>
<h2>v1.2.0</h2>
<h1>Bug Fixes</h1>
<ul>
<li>Fall back to GNU tar on older versions of Windows that do not have BSD tar installed (<a href="https://github-redirect.dependabot.com/actions/cache/issues/252">#252</a>)</li>
<li>Fixed chunk upload retry logic (<a href="https://github-redirect.dependabot.com/actions/cache/issues/305">#305</a>)</li>
</ul>
<h1>Improvements</h1>
<ul>
<li>Improved reliability of the download cache APIs (<a href="https://github-redirect.dependabot.com/actions/cache/issues/269">#269</a>)</li>
<li>Added retries to API calls that failed due to retryable errors (<a href="https://github-redirect.dependabot.com/actions/cache/issues/306">#306</a>)</li>
<li>Improved error handling during both cache upload (<a href="https://github-redirect.dependabot.com/actions/cache/issues/300">#300</a>) and download (<a href="https://github-redirect.dependabot.com/actions/cache/issues/284">#284</a>)</li>
</ul>
<h2>v1.1.2</h2>
<h1>Other</h1>
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/actions/cache/commit/c64c572235d810460d0d6876e9c705ad5002b353"><code>c64c572</code></a> Catch and log unhandled exceptions stemming from closed file descriptor (<a href="https://github-redirect.dependabot.com/actions/cache/issues/596">#596</a>)</li>
<li><a href="https://github.com/actions/cache/commit/cc2d767a726ddd654506e76169ec14b20dc75915"><code>cc2d767</code></a> Update Rust directories recommended for caching (<a href="https://github-redirect.dependabot.com/actions/cache/issues/433">#433</a>)</li>
<li><a href="https://github.com/actions/cache/commit/2fa955d825a29821e73ec064792122ea9f70e573"><code>2fa955d</code></a> Update examples.md (<a href="https://github-redirect.dependabot.com/actions/cache/issues/588">#588</a>)</li>
<li><a href="https://github.com/actions/cache/commit/3a696372f2ec10535e4c026a4fdae5fcca629e4a"><code>3a69637</code></a> elixir typo - stray parenthesis (<a href="https://github-redirect.dependabot.com/actions/cache/issues/569">#569</a>)</li>
<li><a href="https://github.com/actions/cache/commit/366e5ba0224e0ebd6fba2a453d108cb20e734946"><code>366e5ba</code></a> Update cache key for Elixir (<a href="https://github-redirect.dependabot.com/actions/cache/issues/568">#568</a>)</li>
<li><a href="https://github.com/actions/cache/commit/8d3f2fc3ce25d6c95a1297ce8d93f9c3c3ac8f00"><code>8d3f2fc</code></a> Update dependencies (<a href="https://github-redirect.dependabot.com/actions/cache/issues/565">#565</a>)</li>
<li><a href="https://github.com/actions/cache/commit/1a9e2138d905efd099035b49d8b7a3888c653ca8"><code>1a9e213</code></a> Update cache module to v1.0.7 (<a href="https://github-redirect.dependabot.com/actions/cache/issues/562">#562</a>)</li>
<li><a href="https://github.com/actions/cache/commit/981fa981ed950efef5277587ee4ba0eead30cadf"><code>981fa98</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/actions/cache/issues/469">#469</a> from ericmj/patch-1</li>
<li><a href="https://github.com/actions/cache/commit/4498c5b4d8b0673dbc7d9731bc11d9cc5a2c6087"><code>4498c5b</code></a> Drop the example based on using pip's internals (<a href="https://github-redirect.dependabot.com/actions/cache/issues/519">#519</a>)</li>
<li><a href="https://github.com/actions/cache/commit/4134e6de47156381d31ff74f8aabf86718858f70"><code>4134e6d</code></a> It is not recommended to cache node_modules (<a href="https://github-redirect.dependabot.com/actions/cache/issues/537">#537</a>)</li>
<li>Additional commits viewable in <a href="https://github.com/actions/cache/compare/v1...v2.1.6">compare view</a></li>
</ul>
</details>
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</details>

## 🛠️ PR Summary

<sub>Made with ❤️ by [Ultralytics Actions](https://github.com/ultralytics/actions)<sub>

### 🌟 Summary
Upgrade of GitHub Actions pip caching for better efficiency.

### 📊 Key Changes
- Updated the GitHub Actions cache dependency from `actions/cache@v1` to `actions/cache@v2.1.6`.

### 🎯 Purpose & Impact
- The update aims to enhance the caching mechanism for pip in the CI (Continuous Integration) testing workflow.
- Users can expect more reliable and faster build/test times due to the improved caching strategy. 🚀