Update dependency firebase-admin to v7.2.0 (#15)

Author: renovate[bot]

package-lock.json

@@ -14,7 +14,7 @@
     "dev": "next src/app"
   },
   "dependencies": {
-    "firebase-admin": "7.1.1",
+    "firebase-admin": "7.2.0",
     "firebase-functions": "2.2.1",
     "next": "8.0.4",
     "react": "16.8.6",