[youtube] Correctly disable polymer on all requests

Rather than just the one that use the _download_webpage helper. The need
for this was made apparent by 0fe7783e, which refactored
_download_json in a way that completely avoids the use of
_download_webpage, thus breaking youtube.

Fixes #16323

youtube_dl/extractor/youtube.py

@@ -246,9 +246,9 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
 
         return True
 
-    def _download_webpage(self, *args, **kwargs):
+    def _download_webpage_handle(self, *args, **kwargs):
         kwargs.setdefault('query', {})['disable_polymer'] = 'true'
-        return super(YoutubeBaseInfoExtractor, self)._download_webpage(
+        return super(YoutubeBaseInfoExtractor, self)._download_webpage_handle(
             *args, **compat_kwargs(kwargs))
 
     def _real_initialize(self):