Bump next from 15.1.7 to 15.2.3

Bumps [next](https://github.com/vercel/next.js) from 15.1.7 to 15.2.3.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.1.7...v15.2.3)

---
updated-dependencies:
- dependency-name: next
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

frontend/package.json

@@ -28,7 +28,7 @@
     "jwt-decode": "^4.0.0",
     "markdown-it": "^13.0.1",
     "mimetext": "^3.0.24",
-    "next": "^15.2.1",
+    "next": "^15.2.3",
     "next-client-cookies": "^2.0.1",
     "nhs-notify-backend-client": "*",
     "nhs-notify-web-template-management-utils": "*",