Fix musicbrainz genres fetching

[JOJ0]

• genres are now called tags
• tags needs to be in "mb fetch includes"
• release-group has them
• release has them
• and recording as well but we don't use them
• not sure what this outdated check was doing, it looked at "recordings" in the valid list even though genre fetching is only included in the album_info code and not track_info 🤷
• see musicbrainz.VALID_INCLUDES for reference

Description

Fixes #X.

(...)

To Do

• Documentation. (If you've added a new command-line flag, for example, find the appropriate page under docs/ to describe it.)
• Changelog. (Add an entry to docs/changelog.rst to the bottom of one of the lists near the top of the document.)
• Tests. (Very much encouraged but not strictly required.)

[github-actions]

Thank you for the PR! The changelog has not been updated, so here is a friendly reminder to check if you need to add an entry.

[JOJ0]

While looking at #5606 I realized that genres fetching from musicbrainz is actually broken since.....I don't know :-/

[snejus]

I have a feeling this line doesn't behave as intended. Did you consider adding tests?

[JOJ0]

Nope actually I didn't, just trying to quickly fix what was broken and on to more important things :-)

Actually I'm rather wondering why these kinds of checks are of any use here. What is there purpose? Why is it useful to check if something is valid if it is allowed to get silently broken anyway? Nobody will notice when this check is false and the outcome just is: "there are no genres for this album". No error no nothing. Useless in my opinion.

This is by the way the valid_includes constants dict:

https://github.com/alastair/python-musicbrainzngs/blob/1638c6271e0beb9560243c2123d354461ec9f842/musicbrainzngs/musicbrainz.py#L36-L84