Fix several wrong pootle merges between different languages

Because of "who knows" and lots of project ID confusion in pootle, it appears that for some updates from template, Pootle actually updated the translation file against a different language.
Files affected that I'm aware of right now (in `po/uh/`):
- af.po
- ca@valencia.po
- da.po
- el.po
- hi.po
- ja.po

This pull requests hopefully removes as many wrong translations as possible while keeping most correct ones.

Manually reviewed all but `af` which is re-initialized as empty (there were no legit changes).