Remove `--ignore-missing-imports` flag from mypy pre-commit hook

[dav3r]

💡 Summary

Remove the --ignore-missing-imports flag from our mypy pre-commit hook.

Motivation and context

The mypy pre-commit hook that we use includes the --ignore-missing-imports flag by default, but we want to override that behavior. This will give us better mypy analysis and force us to document where type stubs are unavailable/missing.

For more context, see this discussion.

Implementation notes

Don't forget to put a helpful comment in the .pre-commit-config.yaml section explaining why we are adding this (or something like it):

args:
  # Add a useful comment here
  - --scripts-are-modules

Acceptance criteria

• [ ] Our mypy pre-commit hook no longer includes the --ignore-missing-imports flag