[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

jupyter_server/serverapp.py

@@ -3242,7 +3242,7 @@ async def _cleanup(self) -> None:
             self.http_server.stop()
         if hasattr(self, "metrics_server"):
             # Stop the metrics server if it's running
-            if hasattr(self.metrics_server, 'stop'):
+            if hasattr(self.metrics_server, "stop"):
                 self.metrics_server.stop()
 
     def start_ioloop(self) -> None: