gh-38738: activate linter check of E275 and clean one file
this is fixing the last warning for
E275 missing whitespace after keyword
then cut some lines in the modified file and activate the check for E275
in our linter
### :memo: Checklist
- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
URL: https://github.com/sagemath/sage/pull/38738
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert, Frédéric Chapoton, Kwankyu Lee
