gh-36854: various details in categories (ruff C4 and UP02)
fixing a few `ruff` suggestions in `categories` (UP02 and C4 ruff codes)
### :memo: Checklist
- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
URL: https://github.com/sagemath/sage/pull/36854
Reported by: Frédéric Chapoton
Reviewer(s): Matthias Köppe
