Patching conf.py due to Sphinx deprecating config manipulation

[snarayan21]

Description of changes:

Required by Oct 7 due to Sphinx deprecation of config manipulation. More info here: https://about.readthedocs.com/blog/2024/07/addons-by-default/

Patch similar to composer's: https://github.com/mosaicml/composer/pull/3491/files

Issue #, if available:

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