chore(deps): update actions/setup-python action to v6 (#1316) #3019

Job	Run time
Integration Tests (pdm.minimal.lock)	52s
Integration Tests (pdm.lock)	56s
test_min_deps (macos-latest)	1m 10s
test_min_deps (ubuntu-latest)	41s
test (3.9, ubuntu-latest)	1m 21s
test (3.10, windows-latest)	1m 47s
test (3.13, ubuntu-latest)	1m 28s
test (3.11, macos-latest)	1m 7s
test (3.13, macos-latest)	47s
test (3.12, ubuntu-latest)	1m 26s
test (3.12, macos-latest)	55s
test (3.10, macos-latest)	1m 44s
test (3.9, windows-latest)	1m 50s
test (3.11, ubuntu-latest)	1m 13s
test (3.11, windows-latest)	2m 13s
test (3.13, windows-latest)	1m 45s
test (3.9, macos-latest)	1m 56s
test (3.12, windows-latest)	1m 50s
test_min_deps (windows-latest)	1m 20s
test (3.10, ubuntu-latest)	1m 26s
Combine & check coverage	15s
	28m 2s

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