tests

Bump min Python version for GHA (and fix spurious CI error) #5761

Job	Run time
collateral (diffcov)	6m 39s
test_cygwin (39, windows-latest)	9m 40s
collateral (docs)	1m 57s
test (3.9, ubuntu-latest)	1m 32s
test (3.9, macos-latest)	1m 38s
test (3.9, windows-latest)	1m 16s
test (3.13, ubuntu-latest)	1m 33s
test (3.13, macos-latest)	1m 40s
test (3.13, windows-latest)	1m 18s
test (3.10, ubuntu-latest)	1m 32s
test (3.11, ubuntu-latest)	1m 34s
test (3.12, ubuntu-latest)	1m 34s
test (3.14, ubuntu-latest)	1m 32s
test (pypy3.10, ubuntu-latest, stdlib)	1m 31s
test (ubuntu-latest, 3.10, stdlib)	1m 33s
test (3.8, macos-13)	1m 15s
integration-test	0s
check	2s
release	1s
	37m 47s

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