Bump next from 12.3.1 to 15.1.6 in /website

Bumps [next](https://github.com/vercel/next.js) from 12.3.1 to 15.1.6.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](https://github.com/vercel/next.js/compare/v12.3.1...v15.1.6)

---
updated-dependencies:
- dependency-name: next
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

website/package.json

@@ -8,7 +8,7 @@
     "@hashicorp/platform-content-conformance": "^0.0.12",
     "dart-linkcheck": "^2.0.15",
     "husky": "^9.0.7",
-    "next": "^12.3.1",
+    "next": "^15.1.6",
     "prettier": "^3.2.4"
   },
   "main": "index.js",