gh-37397: fix some ruff suggestions in cluster_algebra_quiver
this was scripted using `ruff` for the codes `UP` and `C4` in the
cluster folder.
Plus a few hand-made changes about pep8
### :memo: Checklist
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URL: https://github.com/sagemath/sage/pull/37397
Reported by: Frédéric Chapoton
Reviewer(s): Travis Scrimshaw
