doc: remove style instruction that is not followed

Remove style guide instruction to place punctuation inside parentehses
and quotation marks. Those are not universally correct and we do not
follow those rules in cases where they are not correct.

PR-URL: #23346
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>

doc/STYLE_GUIDE.md

@@ -24,8 +24,6 @@
     clause — a subject, verb, and an object.
   * Outside of the wrapping element if the wrapping element contains only a
     fragment of a clause.
-* Place end-of-sentence punctuation inside wrapping elements — periods go
-  inside parentheses and quotes, not after.
 * Documents must start with a level-one heading.
 * Prefer affixing links to inlining links — prefer `[a link][]` to
   `[a link](http://example.com)`.