mypy

Add shebang documentation for PyManager 26.3b1 (GH-150931) #21732

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

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