[core] Deprecate internal Youtubedl-no-compression header (#6876)

Authored by: coletdjnz

yt_dlp/utils/_utils.py

@@ -1308,25 +1308,12 @@ def _create_http_connection(ydl_handler, http_class, is_https, *args, **kwargs):
     return hc
 
 
-def handle_youtubedl_headers(headers):
-    filtered_headers = headers
-
-    if 'Youtubedl-no-compression' in filtered_headers:
-        filtered_headers = {k: v for k, v in filtered_headers.items() if k.lower() != 'accept-encoding'}
-        del filtered_headers['Youtubedl-no-compression']
-
-    return filtered_headers
-
-
 class YoutubeDLHandler(urllib.request.HTTPHandler):
     """Handler for HTTP requests and responses.
 
     This class, when installed with an OpenerDirector, automatically adds
-    the standard headers to every HTTP request and handles gzipped and
-    deflated responses from web servers. If compression is to be avoided in
-    a particular request, the original request in the program code only has
-    to include the HTTP header "Youtubedl-no-compression", which will be
-    removed before making the real request.
+    the standard headers to every HTTP request and handles gzipped, deflated and
+    brotli responses from web servers.
 
     Part of this code was copied from:
 
@@ -1389,11 +1376,13 @@ class YoutubeDLHandler(urllib.request.HTTPHandler):
             if h.capitalize() not in req.headers:
                 req.add_header(h, v)
 
+        if 'Youtubedl-no-compression' in req.headers:  # deprecated
+            req.headers.pop('Youtubedl-no-compression', None)
+            req.add_header('Accept-encoding', 'identity')
+
         if 'Accept-encoding' not in req.headers:
             req.add_header('Accept-encoding', ', '.join(SUPPORTED_ENCODINGS))
 
-        req.headers = handle_youtubedl_headers(req.headers)
-
         return super().do_request_(req)
 
     def http_response(self, req, resp):