chore(deps): bump next from 14.2.18 to 14.2.21 in /nextjs-app-v14

Bumps [next](https://github.com/vercel/next.js) from 14.2.18 to 14.2.21.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v14.2.18...v14.2.21)

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

Signed-off-by: dependabot[bot] <[email protected]>

nextjs-app-v14/package.json

@@ -19,7 +19,7 @@
     "@justeattakeaway/pie-webc": "0.6.0",
     "@lit-labs/nextjs": "0.2.0",
     "@lit/react": "1.0.6",
-    "next": "14.2.18",
+    "next": "14.2.21",
     "react": "18.3.1",
     "react-dom": "18.3.1",
     "sass": "1.81.0"