Fix CI for Gymnasium v0.29.0

[rodrigodelazcano]

Description

1. Fix CI issue with mujoco_py by specifying the cython version. Same issue as in Gymnasium, fixed in Limit cython version on mujoco-py option install Gymnasium#616.
2. Close franka_config.xml after opening.
3. Fix Deprecation Warning from numpy==1.25.0 in Franka environment

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes