add complex to scalar to avoid raising warnings by linters

[aaishwarymishra]

Proposed changes

This pull request makes a small change to the python/mlx/_stub_patterns.txt file by updating the scalar type alias to include the complex type in addition to int, float, and bool. This allows the codebase to support complex numbers where scalar is used.

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

[zcbenz]

Thanks!