Fix grammar in comments and docstrings (#194624)

Sweep of grammar and typo fixes in comments, docstrings, and doctest
annotations across Dynamo, Inductor, autograd, JIT backends, lazy core,
headeronly complex, and nn.Upsample. Fixes subject-verb agreement,
missing words, misplaced words, and stray possessive apostrophes
("Mirror's" -> "Mirrors", "similar as" -> "similar to").

No functional changes: every edit is inside a comment, docstring, or a
doctest comment line. Behavior, APIs, and generated code are untouched.

Test Plan: comment-only change, so no runtime behavior to exercise. Verified
nothing outside comments changed and that lint passes:

```
git diff -U0 | grep '^[+-]' | grep -vE '^(\+\+\+|---)'
lintrunner -a
```

Authored with the assistance of an AI coding agent (Claude Code).

Pull Request resolved: https://github.com/pytorch/pytorch/pull/194624
Approved by: https://github.com/aorenste