[extractor/rtve.es:live] Fix title and video id discovering

[mondeja]

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Description of your pull request and other information

Update title and video id discovering process for RTVE.es live streams.

[alexanderadam]

This PR looks reasonable to me. Is it just because of a lack of time that it wasn't merged yet or is it something that still need to be changed?

By the way, would it be possible to fetch/embed the subtitles as well? Similar to the other platforms where --list-subs, --write-sub, --all-subs etc is working?

It seems that there was once another Python script for this.