tests

Update codecov/codecov-action to v4 #33

Job	Run time
test_cygwin (39, windows-latest)	19m 11s
test (3.8, ubuntu-latest)	5m 52s
collateral (diffcov)	5m 57s
test (3.8, macos-latest)	11m 4s
collateral (docs)	58s
test (3.8, windows-latest)	17m 37s
test (3.11, ubuntu-latest)	3m 54s
test (3.11, macos-latest)	10m 3s
test (3.11, windows-latest)	11m 45s
test (3.12, ubuntu-latest)	6m 43s
test (3.12, macos-latest)	15m 32s
test (3.12, windows-latest)	11m 38s
test (3.9, ubuntu-latest)	6m 24s
test (3.10, ubuntu-latest)	3m 54s
test (pypy3.10, ubuntu-latest, stdlib)	6m 18s
test (ubuntu-latest, 3.10, stdlib)	4m 6s
integration-test	0s
check	2s
release	0s
	2h 20m 58s

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