Bump actions/setup-python from 4 to 5 #158

Job	Run time
Ensure cogified files are up-to-date	12s
📦 Build the source distribution	13s
Verify dev env on ubuntu-latest	23s
Verify dev env on windows-latest	51s
Build docs & run doctests	25s
Tests on 3.8	38s
Mypy on 3.8	19s
Tests on 3.9	22s
Mypy on 3.9	19s
Tests on 3.10	26s
Mypy on 3.10	15s
Tests on 3.11	20s
Mypy on 3.11	18s
Tests on 3.12	22s
Mypy on 3.12	18s
Combine & check coverage	8s
required-checks-pass	2s
	5m 51s

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