chore(dependency): update dependency @google-cloud/firestore to v8

Author: renovate[bot]

packages/firestore/package.json

@@ -35,7 +35,7 @@
   },
   "homepage": "https://github.com/grammyjs/storages/tree/main/packages/firestore#readme",
   "devDependencies": {
-    "@google-cloud/firestore": "^6.6.0"
+    "@google-cloud/firestore": "^8.0.0"
   },
   "keywords": [
     "grammy",