Update dependency firebase-functions to v7 (#61)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

functions/package-lock.json

@@ -16,7 +16,7 @@
   "main": "lib/handlePlayNotification.js",
   "dependencies": {
     "firebase-admin": "^13.0.0",
-    "firebase-functions": "^6.0.0"
+    "firebase-functions": "^7.0.0"
   },
   "devDependencies": {
     "@eslint/compat": "^1.4.0",