Removes unused google-auth-library dependency

Author: KevyVo

samples/mastra-nextjs/app/package.json

@@ -32,7 +32,6 @@
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "dotenv": "^16.4.7",
-    "google-auth-library": "^10.5.0",
     "lucide-react": "^0.475.0",
     "next": "^16.0.3",
     "next-safe-action": "^7.10.3",