Disable warn_unused_ignores again (#60480)
Summary:
Fixes https://github.com/pytorch/pytorch/pull/60006#issuecomment-866130657.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60480
Test Plan: Run `mypy --config mypy-strict.ini` with [`ruamel.yaml`](https://pypi.org/project/ruamel.yaml/) installed.
Reviewed By: zhouzhuojie
Differential Revision: D29307823
Pulled By: samestep
fbshipit-source-id: 97fa4b7dad0465c269411c48142b22ce751bf830
