chore: Update PR template to match Mergify bugfix

Mergify fixed the bug we were using to not have to duplicate the
PR title into the PR body in the custom squash-merge message.

Update PR template to match.

Author: rix0rrr

Diff for: .github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,7 @@
 ### Commit Message
+COMMIT TITLE HERE (copy from PR title, keep in sync)
 
-COMMIT MESSAGE HERE (preserve newline after "Commit Message" heading)
-
+COMMIT MESSAGE HERE
 ### End Commit Message
 
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