Improve pull request template

[Ainali]

Description

For many of my latest PRs which have been updating queries to either match new modeling choices on Wikidata or a changed reality (new ministries etc.) the types have not felt great. It is neither a bug nor a new feature. Could we add a type called query maintenance or something similar?

[Abbe98]

We should properly have an "other" option.

[Ainali]

Come to think on it, should it really be a checkbox? Wouldn't a reminder text about setting a label be better? (Can new users see the available labels?)

[Abbe98]

Should external contributors be responsible for classifying/labeling pull requests to begin with? It's not like that is the task which saves us time...

[Ainali]

That's a really good point. Perhaps we should remove that entire section from the template, and then the first reviewer assigns labels if needed.

[Abbe98]

Yeah I think so.