Change 'w.r.t.' to 'wrt' in function docstrings to fix doc rendering (#100028)
Fixes #72428 according to decision reached in comments.
I've left other instances of `w.r.t.` in tact (e.g. in parameter/return descriptions, in comments, etc) because there were many, and I didn't' want to go out-of-scope. That being said, I'm happy to change those as well if we'd prefer the consistency!
I've also fixed a typo that I came across while grepping for instances.
Will update with screenshots once docs are built.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/100028
Approved by: https://github.com/albanD
