chore(deps): update actions/checkout action to v7 (#1453) #3368

Job	Run time
test_min_deps (macos-latest)	28s
Integration Tests (pdm.minimal.lock)	30s
test_min_deps (ubuntu-latest)	35s
test_min_deps (windows-latest)	1m 21s
test (3.11, macos-latest)	33s
test (3.13, ubuntu-latest)	1m 11s
test (3.12, windows-latest)	1m 42s
Integration Tests (pdm.lock)	24s
test (3.14, windows-latest)	1m 40s
test (3.13, windows-latest)	2m 45s
test (3.11, windows-latest)	1m 34s
test (3.13, macos-latest)	29s
test (3.14, macos-latest)	32s
test (3.12, macos-latest)	33s
test (3.11, ubuntu-latest)	47s
test (3.14, ubuntu-latest)	1m 1s
test (3.12, ubuntu-latest)	54s
Combine & check coverage	10s
	17m 9s

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