[twitch] Prefer source format (closes #20850)

youtube_dl/extractor/twitch.py

@@ -134,12 +134,12 @@ def login_step(page, urlh, note, data):
     def _prefer_source(self, formats):
         try:
             source = next(f for f in formats if f['format_id'] == 'Source')
-            source['preference'] = 10
+            source['quality'] = 10
         except StopIteration:
             for f in formats:
                 if '/chunked/' in f['url']:
                     f.update({
-                        'source_preference': 10,
+                        'quality': 10,
                         'format_note': 'Source',
                     })
         self._sort_formats(formats)