Fix the formatting script: do not try to update a GitHub PR without checking for should_update_gh (llvm#159276)

Author: joker-eph

llvm/utils/git/code-format-helper.py

@@ -173,7 +173,8 @@ def run(self, changed_files: List[str], args: FormatArgs) -> bool:
                 f":warning: The {self.friendly_name} failed without printing "
                 "a diff. Check the logs for stderr output. :warning:"
             )
-            self.update_pr(comment_text, args, create_new=False)
+            if should_update_gh:
+                self.update_pr(comment_text, args, create_new=False)
             return False