Make mypy_wrapper.py accept multiple filenames (#57998)
Summary:
A followup to https://github.com/pytorch/pytorch/issues/57752.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57998
Test Plan:
```
mypy --config=mypy-strict.ini
python tools/test/test_mypy_wrapper.py
python tools/test/test_actions_local_runner.py -k mypy
```
Reviewed By: driazati
Differential Revision: D28338531
Pulled By: samestep
fbshipit-source-id: ae31e3fa4a2b8060c200f9a13f768beaf2f55694
