Bump astro from 4.8.0 to 6.1.6 in /site

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 4.8.0 to 6.1.6.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/astro/CHANGELOG-v4.md)
- [Commits](https://github.com/withastro/astro/commits/astro@6.1.6/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 6.1.6
  dependency-type: direct:production
...

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

Author: dependabot[bot]

site/package.json

@@ -39,7 +39,7 @@
     "@astrojs/sitemap": "^3.1.4",
     "@astrojs/svelte": "^5.4.0",
     "@sanity/client": "^6.18.0",
-    "astro": "^4.8.0",
+    "astro": "^6.1.6",
     "astro-portabletext": "^0.10.0",
     "bcrypt": "^5.1.1",
     "canvas-confetti": "^1.9.3",