docs: fill migration guide gaps surfaced by automated upgrade eval #1809

Job	Run time
checks / pre-commit	29s
checks / readme-snippets	10s
checks / test (3.10, locked, windows-latest)	2m 26s
checks / test (3.12, lowest-direct, windows-latest)	3m 49s
checks / test (3.11, locked, ubuntu-latest)	50s
checks / test (3.11, lowest-direct, ubuntu-latest)	55s
checks / test (3.13, lowest-direct, windows-latest)	2m 53s
checks / test (3.11, lowest-direct, windows-latest)	2m 47s
checks / test (3.10, lowest-direct, ubuntu-latest)	55s
checks / test (3.10, locked, ubuntu-latest)	51s
checks / test (3.13, lowest-direct, ubuntu-latest)	53s
checks / test (3.14, lowest-direct, windows-latest)	2m 26s
checks / test (3.14, locked, ubuntu-latest)	2m 27s
checks / test (3.11, locked, windows-latest)	2m 42s
checks / test (3.13, locked, windows-latest)	2m 50s
checks / test (3.10, lowest-direct, windows-latest)	2m 39s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 5s
checks / test (3.13, locked, ubuntu-latest)	50s
checks / test (3.12, locked, windows-latest)	3m 28s
checks / test (3.14, locked, windows-latest)	3m 25s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 24s
checks / test (3.12, locked, ubuntu-latest)	54s
all-green	5s
	41m 13s

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