deps(example): bump ai

Bumps the dependencies group in /examples/nextjs-openai with 1 update: [ai](https://github.com/vercel/ai).


Updates `ai` from 4.0.6 to 4.0.7
- [Release notes](https://github.com/vercel/ai/releases)
- [Changelog](https://github.com/vercel/ai/blob/main/CHANGELOG.md)
- [Commits](https://github.com/vercel/ai/compare/ai@4.0.6...ai@4.0.7)

---
updated-dependencies:
- dependency-name: ai
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: dependencies
...

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

examples/nextjs-openai/package.json

@@ -11,7 +11,7 @@
   "dependencies": {
     "@ai-sdk/openai": "^1.0.5",
     "@arcjet/next": "file:../../arcjet-next",
-    "ai": "^4.0.6",
+    "ai": "^4.0.7",
     "next": "15.0.3",
     "openai": "^4.73.1",
     "openai-chat-tokens": "^0.2.8",