remove ffpmeg version specification in workflow file

This means that, currently, Github actions will be using version 7 of ffmpeg, while locally ffmpeg 4 will be installed. This is because ffmpeg 6 gives errors, and ffmpeg 7 is not available, yet, using conda. We will change this in the near future.

.github/workflows/python_package.yml

@@ -21,8 +21,6 @@ jobs:
     - uses: actions/checkout@v4
     - name: setup-ffmpeg
       uses: FedericoCarboni/setup-ffmpeg@v3
-      with:
-        ffmpeg-version: 4.2.2
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
       with: