Fix RAdam docstring on LR default value (#69186)
Summary:
Fixes #{issue number}
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69186
Reviewed By: albanD
Differential Revision: D32759614
Pulled By: H-Huang
fbshipit-source-id: b11819c50156a538cd6003e9cddde0390c853f67
