fix(deps): update dependency firebase-admin to v12

Author: renovate[bot]

functions/package.json

@@ -13,7 +13,7 @@
   },
   "dependencies": {
     "express": "4.17.1",
-    "firebase-admin": "9.11.1",
+    "firebase-admin": "12.0.0",
     "firebase-functions": "3.15.7"
   },
   "devDependencies": {