Fixed: black screen rendering for MPE env in rgb_array mode

[cibeah]

Description

Fixes #864 by drawing on pygame screen before extracting the image for rgb_array mode. Only calls pygame.surfarray.pixels3d when needed.

Not sure if a new unit test is needed, can add if necessary !

Type of change

• Bug fix (non-breaking change which fixes an issue)

Screenshots

Please attach before and after screenshots of the change if applicable.

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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

[jjshoots]

Apologies for necro-reviewing this PR, but just a small comment. In addition, could you update to the latest version of master?