Try to fix good-first-issue bot (llvm#71816)

The previous code was just overriding the `comment` variable. Fix this by writing two comments if necessary instead.

Author: tbaederr

llvm/utils/git/github-automation.py

@@ -78,12 +78,13 @@ def run(self) -> bool:
         if not team:
             print(f"couldn't find team named {self.team_name}")
             return False
+
         comment = ""
         if team.slug == "issue-subscribers-good-first-issue":
             comment = "{}\n".format(beginner_comment)
+            self.issue.create_comment(comment)
 
         body = escape_description(self.issue.body)
-
         comment = f"""
 @llvm/{team.slug}