Update to Python 3.11 in documentation

[radarhere]

Suggestion for python-pillow#9750

[codspeed-hq]

Merging this PR will not alter performance

✅ 345 untouched benchmarks
⏩ 2 skipped benchmarks¹

---

_{Comparing radarhere:rm-3.10 (4955fb4) with rm-3.10 (db8e579)²}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on rm-3.10 (ee5464b) during the generation of this report, so db8e579 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩