Update dependency express to ^4.21.1

Author: mend-for-github-com[bot]

package.json

@@ -13,6 +13,6 @@
         "@vonage/server-sdk": "^3.6.0",
         "airtable": "^0.8.1",
         "dotenv": "^16.3.1",
-        "express": "^4.18.2"
+        "express": "^4.21.1"
     }
 }