[formatsort] Remove misuse of 'preference'

'preference' is to be used only when the format is better that ALL qualities of a lower preference irrespective of ANY sorting order the user requests. See deezer.py for correct use of this

In the older sorting method, `preference`, `quality` and `language_preference` were functionally almost equivalent. So these disparities doesn't really matter there

Also, despite what the documentation says, the default for `preference` was actually 0 and not -1. I have tried to correct this and also account for it when converting `preference` to `quality`

youtube_dlc/extractor/nba.py

@@ -303,7 +303,7 @@ class NBABaseIE(NBACVPBaseIE):
                 formats.append({
                     'format_id': 'source',
                     'url': source_url,
-                    'preference': 1,
+                    'quality': 1,
                 })
 
             m3u8_url = video.get('m3u8')