Update python-package.yml

Author: StoneT2000

.github/workflows/python-package.yml

@@ -30,6 +30,7 @@ jobs:
           python -m pip install .[test]
           python -m pip install flake8 pytest
           if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+          pip install mujoco
       - name: Clone mujoco_menagerie repository into the tests/ folder
         run: |
           git clone https://github.com/google-deepmind/mujoco_menagerie