Bump @astrojs/vercel from 8.0.7 to 8.1.5

Bumps [@astrojs/vercel](https://github.com/withastro/astro/tree/HEAD/packages/integrations/vercel) from 8.0.7 to 8.1.5.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/integrations/vercel/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/@astrojs/vercel@8.1.5/packages/integrations/vercel)

---
updated-dependencies:
- dependency-name: "@astrojs/vercel"
  dependency-version: 8.1.5
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

landing/package.json

@@ -16,7 +16,7 @@
     "@astrojs/rss": "^4.0.11",
     "@astrojs/sitemap": "^3.2.1",
     "@astrojs/tailwind": "^6.0.0",
-    "@astrojs/vercel": "^8.0.7",
+    "@astrojs/vercel": "^8.1.5",
     "@polar-sh/sdk": "^0.20.2",
     "astro": "^5.2.4",
     "shepherd.js": "workspace:*",