deps(example): bump @clerk/nextjs

Bumps the dependencies group with 1 update in the /examples/nextjs-clerk-shield directory: [@clerk/nextjs](https://github.com/clerk/javascript/tree/HEAD/packages/nextjs).


Updates `@clerk/nextjs` from 6.9.10 to 6.9.12
- [Release notes](https://github.com/clerk/javascript/releases)
- [Changelog](https://github.com/clerk/javascript/blob/main/packages/nextjs/CHANGELOG.md)
- [Commits](https://github.com/clerk/javascript/commits/@clerk/[email protected]/packages/nextjs)

---
updated-dependencies:
- dependency-name: "@clerk/nextjs"
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: dependencies
...

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

examples/nextjs-clerk-shield/package.json

@@ -10,7 +10,7 @@
   },
   "dependencies": {
     "@arcjet/next": "file:../../arcjet-next",
-    "@clerk/nextjs": "^6.9.10",
+    "@clerk/nextjs": "^6.9.12",
     "next": "15.1.4",
     "react": "^19",
     "react-dom": "^19"