fix documentation of car-racing continuous argument

[pertakle]

Description

The description of the continuous argument in the car_racing environment states:

`continuous=True` converts the environment to use discrete action space.

However, this is incorrect. Setting continuous=True actually enables a continuous action space, not a discrete one. This PR corrects the misleading comment.

Type of change

Please delete options that are not relevant.

• Documentation only change (no code changed)

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

[pseudo-rnd-thoughts]

Thanks for the pr but continuous should stay as True, rather the description should be updated to accurately reflect its implementation meaning