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#### Describe the bug
Some servers are not sending a zlib header in their deflated data. CURL had the same problem and implemented a "fix" for it: https://github.com/curl/curl/blob/5c932f8fe9dad94a7417702958ffa9e8db67c549/lib/content_encoding.c#L227-L229

Axios is also returning a `Z_DATA_ERROR` in this case.

#### To Reproduce

Use axios to request a page without a zlib header in the deflated data (e.g. https://www.konicaminolta.eu/eu-en/about-us/corporate-book) and force it to only accept deflate encoding.

```js
let url = 'https://www.konicaminolta.eu/eu-en/about-us/corporate-book';
let config = {
  headers: { 'Accept-Encoding': 'deflate' }
};

await axios.get(url, config);
```

#### Expected behavior

Getting the correctly inflated data.

#### Environment
 - Axios Version [0.21.1]


#### Additional context/Screenshots


test/unit/adapters/http.js
response.setHeader('Content-Type', 'text/html; charset=UTF-8');
            response.end(body + '1234');
          });
        });
      }).listen(4000, function () {
        // se
        process.env.http_proxy = 'http://localhost:4000/';
        axios.get('http://localhost:4444/').then(function (res) {
          assert.equal(res.data, '45671234', 'should use proxy set by process.env.http_proxy');
          done();
        }).catch(done);
      });
    });
  });
  it('should support HTTPS proxy set via env var', function (done) {
    var options = {
      key: fs.readFileSync(path.join(__dirname, 'key.pem')),
      cert: fs.readFileSync(path.join(__dirname, 'cert.pem'))
    };
    server = https.createServer(options, function (req, res) {
      res.setHeader('Content-Type', 'text/html; charset=UTF-8');
      res.end('12345');
    }).listen(4444, function () {
      proxy = https.createServer(options, function (request, response) {
        var parsed = url.parse(request.url);
        var opts = {
          host: parsed.hostname,
          port: parsed.port,
          path: parsed.path,
          protocol: parsed.protocol,