Suppress typing warnings in get_module_path function

Rationale:
As pkgutil has really poor typing, it is not possible
to make proper typing in this place.
The `# type: SourceFileLoader` was not working here.

Fixes mypy errors:
- package/test_tools/__private/scope/scopes_stack.py:55: error: Item "Loader" of "Optional[Loader]" has no attribute "path"
- package/test_tools/__private/scope/scopes_stack.py:55: error: Item "None" of "Optional[Loader]" has no attribute "path"