fix: upgrade express from 4.20.0 to 4.21.0

Snyk has created this PR to upgrade express from 4.20.0 to 4.21.0.

See this package in npm:
express

See this project in Snyk:
https://app.snyk.io/org/domin737/project/bda5e07c-f593-483d-826d-974f630def86?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot

package-lock.json

@@ -16,7 +16,7 @@
     "cors": "2.8.5",
     "cross-env": "7.0.3",
     "dotenv": "^16.4.5",
-    "express": "^4.19.2",
+    "express": "^4.21.0",
     "firebase": "^10.13.1",
     "firebase-admin": "^12.5.0",
     "gravatar": "^1.8.2",