Docs: update aec_rps.py

[liuzhaoze]

Description

Update code in the documentation.

Type of change

• This change requires a documentation update

Reason

All environments use self.observation_spaces and self.action_spaces to define observation spaces and action spaces, rather than self._observation_spaces and self._action_spaces. So, I think it is necessary to fix it to ensure consistency.

In addition, I modified the observation_space and action_space methods to obtain the observation space and action space through dict self.observation_spaces and self.action_spaces to correspond with the comment on L78.

I did not modify the observation_space and action_space methods in parallel_rps.py because observation spaces and action spaces are defined in them rather than self.observation_spaces and self.action_spaces.

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have run pytest -v and no errors are present.
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I solved any possible warnings that pytest -v has generated that are related to my code to the best of my knowledge.
• 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