Bump next in /examples/next/custom-sitemap-vanilla-wpgraphql/example-app

Bumps [next](https://github.com/vercel/next.js) from 15.4.7 to 15.4.8.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.4.7...v15.4.8)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.4.8
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

examples/next/custom-sitemap-vanilla-wpgraphql/example-app/package.json

@@ -10,7 +10,7 @@
   },
   "dependencies": {
     "@apollo/client": "^3.13.5",
-    "next": "15.4.7",
+    "next": "15.4.8",
     "react": "^19.0.0",
     "react-dom": "^19.0.0"
   },