fix(deps): update dependency mongoose to v6.13.6 [security]

Author: renovate-bot

nodejs/nodejs-guestbook/src/backend/package-lock.json

@@ -12,6 +12,6 @@
     "body-parser": "1.20.2",
     "mongodb": "4.17.1",
     "express": "4.18.2",
-    "mongoose": "6.11.3"
+    "mongoose": "6.13.6"
   }
 }