### Summary

Our setuptools constrain in `pyproject.toml` (listed also in `setup.cfg`) is set to `>= 39.2.0` due to the minimum version available at the time on Ubuntu 18.04.

Now that we have a dependency on Python 3.9 as a minimum, that constraint no longer makes sense, as Python 3.9 is not available on 18.04, and the `dist-packages` `setuptools==39.2.0` compat between deadsnakes python3.9 is non-functional.

This would make Ubuntu 20.04 effectively the minimum supported controller.  The `dist-packages` `setuptools==45.2.0` is functional with the `python3.9` package, and works fine with our packaging.  

This doesn't really grant us anything, since we're waiting for the minimum to eventually be `51.0.0` so we can list the `entry_points` in `pyproject.toml`, but no need to list effectively a non-functional lower bounds. 

### Issue Type

Feature Idea

### Component Name

pyproject.toml

### Additional Information

<!--- Paste example playbooks or commands between quotes below -->
```yaml (paste below)

```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
"""Check that the files we expect to ship are present in the sdist"""
    results = []
    for filename in to_ship_files:
        path = os.path.join(sdist_dir, filename)
        if not os.path.exists(path):
            results.append('%s: File was not added to sdist' % filename)
    
    changelog_files = glob.glob(os.path.join(sdist_dir, 'changelogs/CHANGELOG-v2.[0-9]*.rst'))
    if not changelog_files:
        results.append('changelogs/CHANGELOG-v2.*.rst: Changelog file was not added to the sdist')
    elif len(changelog_files) > 1:
        results.append('changelogs/CHANGELOG-v2.*.rst: Too many changelog files: %s'
                       % changelog_files)
    return results
def check_sdist_files_are_wanted(sdist_dir, to_ship_files):