Enforce modern annotations syntax #4614

Job	Run time
test_cygwin (39, windows-latest)	15m 29s
collateral (diffcov)	6m 8s
test (3.8, ubuntu-latest)	4m 25s
collateral (docs)	2m 5s
test (3.8, windows-latest)	11m 41s
collateral (check-extern)	14s
test (3.12, ubuntu-latest)	6m 15s
test (3.12, macos-latest)	14m 37s
test (3.12, windows-latest)	12m 52s
test (3.9, ubuntu-latest)	4m 11s
test (3.10, ubuntu-latest)	4m 30s
test (3.11, ubuntu-latest)	4m 4s
test (pypy3.10, ubuntu-latest, stdlib)	7m 5s
test (ubuntu-latest, 3.10, stdlib)	4m 0s
test (3.8, macos-13)	6m 24s
integration-test	0s
check	2s
release	0s
	1h 44m 2s

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