Fix typo simple_reference docstring, fix workflows to use python 3.11 by default

[elliottower]

Description

Fixes issues in #1123, see comments there for context about MPE docstring update

Workflows were updated to use v4 of checkout and setup-python just for the sake of future proofing, there were some warnings about old node versions and stuff like that. I also fixed the python version for things like doc build to use python 3.11 instead of 3.9. Pre-commit was doing python 3.12 because the version was unspecified, so that has been fixed as well (tested locally and 3.12 seems to just have issues with flake8, we can wait for 312 support as it was just released last month)

Fixes # (issue), Depends on # (pull request)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

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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

[elliottower]

I also noticed there were some weird extra spaces in some of the YML files, I think it was a mistake from a previous pre-commit thing I had to reformat YML, fixed it to look normal now

[elliottower]

Looks like an agilerl issue but everything else passes, may wait for that PR to merge this