Bump next from 15.5.6 to 15.5.7 in /upload-site (#538)

Bumps [next](https://github.com/vercel/next.js) from 15.5.6 to 15.5.7.
- [Release notes](https://github.com/vercel/next.js/releases)
- [Changelog](https://github.com/vercel/next.js/blob/canary/release.js)
- [Commits](vercel/next.js@v15.5.6...v15.5.7)

---
updated-dependencies:
- dependency-name: next
  dependency-version: 15.5.7
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

upload-site/package-lock.json

@@ -14,7 +14,7 @@
     "@vercel/blob": "^1.1.1",
     "@vercel/speed-insights": "^1.1.0",
     "adm-zip": "^0.5.16",
-    "next": "^15.5.6",
+    "next": "^15.5.7",
     "next-auth": "^4.24.12",
     "octokit": "^4.0.3",
     "react": "^19.0.0",