httpc: fix content-length with a stream

The description of CURLOPT_UPLOAD [1] is confusing:

    If you use PUT to an HTTP 1.1 server, you can upload data without
    knowing the size before starting the transfer if you use chunked
    encoding. You enable this by adding a header like
    "Transfer-Encoding: chunked" with CURLOPT_HTTPHEADER.

In fact, libcurl adds this header itself. Actually we need to avoid
adding this header by libcurl with CURLOPT_INFILESIZE [2].

The CURLOPT_UPLOAD documentation has been updated [3].

1. https://github.com/curl/curl/blob/555bacd6d522bcca497573765056354f4d5d7b33/docs/libcurl/opts/CURLOPT_UPLOAD.3
2. https://curl.se/libcurl/c/httpput.html
3. https://github.com/curl/curl/pull/11300

Closes #8744

NO_DOC=bugfix

(cherry picked from commit e2e5ef4b)