Discourage typo fixes in PR template (microsoft#46908)

* Discourage typo fixes in PR template

Wording taken from [this comment](microsoft#45834 (comment)).

There have been a number of rejected typo fix PRs lately; hopefully this can reduce the amount of typo-fix-rejecting work for the team.

* Tweak typo fix discouragement in PR template

Removed "the same generally applies to other projects" per orta

* Update typo fix discouragement

Author: tjjfvi

.github/pull_request_template.md

@@ -9,6 +9,13 @@ Please verify that:
 
 Refer to CONTRIBUTING.MD for more details.
   https://github.com/Microsoft/TypeScript/blob/main/CONTRIBUTING.md
+
+** Please don't send typo fixes! **
+Please don't send a PR solely for the purpose of fixing a typo, unless that
+typo truly hurts understanding of the text. Each PR represents work for the
+maintainers, and that work should provide commensurate value.
+
+If you're interested in sending a PR, the issue tracker has many issues marked `help wanted`.
 -->
 
 Fixes #