Remove Gym dependency contract to smooth out Gym-side dependency changes

**Is your feature request related to a problem? Please describe.**
I'm changing the Gym dependencies and I need to upstream a corresponding NeMo RL change.

**Describe the solution you'd like**
NeMo RL doesn't error out when Gym changes dependencies

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
Add any other context or screenshots about the feature request here.

AIs:
1. RL pyproject.toml Gym workspace points to Gym directly rather than the Gym-workspace dir
2. Remove the intermediary setup.py and other files inside Gym-workspace
3. Re-uv lock