gh-37245: a few details in combinat folder
namely
- use ruff to fix some containement tests
- add links to some error codes in the doc
### :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/37245
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert, Frédéric Chapoton
