gh-36653: clean E702 etc in integer.pyx
    
some cleanup in the file `integer.pyx`

mostly fixing E702 warnings, and other `cython-lint` warnings

### 📝 Checklist

- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
    
URL: #36653
Reported by: Frédéric Chapoton
Reviewer(s): Matthias Köppe

Author: Release Manager