guzzle@1d46cec
tried to improve the comment but the new content implies an empty header
will be sent.

That is not the case. Quoting from <https://curl.se/libcurl/c/CURLOPT_HTTPHEADER.html>:

    If you add a header with no content as in 'Accept:'
    (no data on the right side of the colon),
    the internally used header is disabled/removed.

Let’s clarify the point is removing the header to get the default '*'
<https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept-Encoding#sect2>:

    *: Matches any content encoding not already listed in the header.
    This is the default value if the header is not present.
    This directive does not suggest that any algorithm is supported
    but indicates that no preference is expressed.

As that was probably intended by the original change that introduced this:
guzzle@1a9ad6b