Update dependencies (shimmy, sphinx), remove sphinx_autodoc_typehints

[araffin]

Description

When we started SB3, Sphinx didn't properly support type hint and we had to rely on a plugin for that.
But from the beginning, it had to be tweaked (see #10) and caused many issues (because of not properly supporting forward references), the latest one being #1720.

The good news is that Sphinx now natively supports type hints and display them nicely.

I also updated the dependencies as issues are now fixed with the latest rtd theme.

The doc built with this PR: https://stable-baselines3.readthedocs.io/en/chores-update-deps/

NOTE: build of the doc was failing on RTD because new keys in the config are required, RL Zoo and SB3 contrib must be updated too.

Motivation and Context

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

• 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 change)
• Documentation (update in the documentation)

Checklist

• I've read the CONTRIBUTION guide (required)
• I have updated the changelog accordingly (required).
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.
• I have opened an associated PR on the SB3-Contrib repository (if necessary)
• I have opened an associated PR on the RL-Zoo3 repository (if necessary)
• I have reformatted the code using make format (required)
• I have checked the codestyle using make check-codestyle and make lint (required)
• I have ensured make pytest and make type both pass. (required)
• I have checked that the documentation builds using make doc (required)

Note: You can run most of the checks using make commit-checks.

Note: we are using a maximum length of 127 characters per line

[ernestum]

LGTM. Great idea to simplify the doc build process!