[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/facebook.py

@@ -619,7 +619,7 @@ class FacebookIE(InfoExtractor):
                         formats.append({
                             'format_id': '%s_%s_%s' % (format_id, quality, src_type),
                             'url': src,
-                            'preference': preference,
+                            'quality': preference,
                         })
             extract_dash_manifest(f[0], formats)
             subtitles_src = f[0].get('subtitles_src')