ytdl_hook.lua: set the title in metadata

93fe7a5526 made global_tags work with all_formats=yes, so do like
suggested in 8ea7aa5471 and set the title via tags.

This makes available in ${metadata/title}, even if you set
--force-media-title separately.

--force-media-title is also set when self_redirecting_url is true, but
tags seem not to be set in this case and I don't know where to find such
videos to test. It was originally added to close #5313, but the URL
linked there no longer loads.