Ignore "Unavailable videos are hidden" warnings from YouTube

[mgedmin]

Description of your pull request and other information

I have a cron script that tries to back up my YouTube favorites playlist (because videos tend to disappear off the net without warning). I recently started using yt-dlp for this purpose. It works very well, except it emits a single warning even in quiet mode:

WARNING: [youtube:tab] YouTube said: INFO - Unavailable videos are hidden

which makes cron send me an email about it.

This PR suppresses that warning.

Template

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