Update dependency firebase-functions to v6

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

functions/package.json

@@ -16,7 +16,7 @@
     "cors": "^2.8.5",
     "dotenv": "^16.4.5",
     "firebase-admin": "^11.8.0",
-    "firebase-functions": "^5.0.1"
+    "firebase-functions": "^6.1.2"
   },
   "devDependencies": {
     "firebase-functions-test": "^3.1.0"