gh-36108: some details in quadratic forms
This is fixing a few minor details in quadratic forms, about
- unused variables found by pylint
- strange re-definitions of ZZ and QQ
### :memo: Checklist
- [x] The title is concise, informative, and self-explanatory.
- [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 accordingly.
URL: https://github.com/sagemath/sage/pull/36108
Reported by: Frédéric Chapoton
Reviewer(s): Kwankyu Lee
