whisper: only package mlx_whisper in the wheel

[Kayvan-Zahiri]

The mlx-whisper 0.4.3 wheel on PyPI installs a top-level build directory next to mlx_whisper:

$ unzip -l mlx_whisper-0.4.3-py3-none-any.whl | awk '{print $4}' | cut -d/ -f1 | sort | uniq -c
     39 build
     17 mlx_whisper
      5 mlx_whisper-0.4.3.dist-info

setup.py uses find_namespace_packages() with no filter. Namespace discovery also picks up directories without an __init__.py, so once a previous build has left whisper/build/lib/mlx_whisper/... behind, the next build packages it as build.lib.mlx_whisper. It reproduces locally: building twice in a clean checkout of main, the second wheel has 12 files under build/.

This restricts discovery to find_namespace_packages(include=["mlx_whisper*"]), which keeps the mlx_whisper.assets data and drops everything else. With the change, both the first and second builds contain only mlx_whisper, and the files under mlx_whisper/ are identical to a first build of main.