fix: sample-app/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-NEXT-8025427

Author: snyk-bot

sample-app/package.json

@@ -16,7 +16,7 @@
     "autoprefixer": "^10.4.15",
     "eslint": "^8.47.0",
     "eslint-config-next": "^13.4.16",
-    "next": "^13.5.4",
+    "next": "^13.5.7",
     "postcss": "^8.4.31",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",