mypy

gh-149887: Install python3t.lib for GIL-enabled Windows install (GH-1… #21375

Job	Run time
Run mypy on Tools/cases_generator	17s
Run mypy on Tools/check-c-api-docs	20s
Run mypy on Tools/clinic	18s
Run mypy on Tools/build	19s
Run mypy on Lib/tomllib	19s
Run mypy on Tools/peg_generator	18s
Run mypy on Tools/jit	19s
Run mypy on Lib/test/libregrtest	21s
Run mypy on Lib/_pyrepl	18s
	2m 49s

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