sage

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gh-37162: refreshing the file projective_subscheme Mostly pep8 formatting, a few `ruff` suggestions done too ### :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/37162 Reported by: Frédéric Chapoton Reviewer(s): Kwankyu Lee