Update actions/checkout action to v6.0.2 #3152

Job	Run time
Dependency	4s
Shellcheck	5s
Cache identify	5s
Prepare	8s
Ruff check and force	10s
Check commit	32s
Run pytest using Python 3.14	35s
Run pytest using Python 3.13	31s
Process test coverage	19s
Run mypy	0s
Process test complexity	12s
Build and publish Python 🐍 distributions 📦 to TestPyPI	12s
	2m 53s

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