Log Message:
youtube-dl: Update to 20190621

Changes:
2019.06.21
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Core
* [utils] Restrict parse_codecs and add theora as known vcodec (#21381)

Extractors
* [youtube] Update signature function patterns (#21469, #21476)
* [youtube] Make --write-annotations non fatal (#21452)
+ [sixplay] Add support for rtlmost.hu (#21405)
* [youtube] Hardcode codec metadata for av01 video only formats (#21381)
* [toutv] Update client key (#21370)
+ [biqle] Add support for new embed domain
* [cbs] Improve DRM protected videos detection (#21339)