Merge branch 'master' of https://github.com/yt-dlp/yt-dlp into ytdlp

* 'master' of https://github.com/yt-dlp/yt-dlp:
  [EmbedSubtitle] Enable for more video extensions
  [utils] certifi: Make sure the pem file exists
  [cleanup] Misc cleanup (#2173)
  [cleanup] Sort imports
  [cleanup] Upgrade syntax
  [cleanup] Mark some compat variables for removal (#2173)
  [cleanup] Remove unused code paths (#2173)
  [cleanup] Remove unused scripts/tests (#2173)
  [FFmpegMetadataPP] Remove `\0` from metadata