fix(deps): update dependency firebase-functions to v4

Author: renovate[bot]

functions/package.json

@@ -14,7 +14,7 @@
   "dependencies": {
     "express": "4.17.1",
     "firebase-admin": "9.11.1",
-    "firebase-functions": "3.15.7"
+    "firebase-functions": "4.5.0"
   },
   "devDependencies": {
     "firebase-functions-test": "0.3.2"