Fix grammatical errors in comments and docstrings (#194564)

Follow-up to #194322, correcting more grammar issues in comments across
Python and C++ sources. No functional changes.

Test Plan: Comment-only changes; no behavior to test. Verified with lint:

```
lintrunner -a
```

This PR was authored with the assistance of an AI coding assistant.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/194564
Approved by: https://github.com/aorenste, https://github.com/kapilsh