Use Optional[dict] instead of dict for files parameter in transcribe.py

[araman0]

In transcribe.py, the files parameter is currently defined as:

files: dict = None,

Since None is a valid default value, it would be more appropriate to use Optional[dict] to explicitly indicate that files can be None:

files: Optional[dict] = None,

This improves type clarity and aligns with Python's type hinting conventions.

Would you consider updating this for better type consistency?
I'm happy to submit a PR if needed.

[MahmoudAshraf97]

I'm open to typing revisions, you can open a PR which continues #1150