build(deps): bump @next/env from 14.2.7 to 15.1.2 in /apps/example

Bumps [@next/env](https://github.com/vercel/next.js/tree/HEAD/packages/next-env) from 14.2.7 to 15.1.2.
- [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/commits/v15.1.2/packages/next-env)

---
updated-dependencies:
- dependency-name: "@next/env"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

apps/example/package.json

@@ -13,7 +13,7 @@
   },
   "dependencies": {
     "@across-protocol/app-sdk": "workspace:*",
-    "@next/env": "^14.2.8",
+    "@next/env": "^15.1.2",
     "@radix-ui/react-dropdown-menu": "^2.1.1",
     "@radix-ui/react-label": "^2.1.0",
     "@radix-ui/react-popover": "^1.1.1",