Bump astro from 5.5.5 to 5.15.6 in /packages/docs

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.5.5 to 5.15.6.
- [Release notes](https://github.com/withastro/astro/releases)
- [Changelog](https://github.com/withastro/astro/blob/main/packages/astro/CHANGELOG.md)
- [Commits](https://github.com/withastro/astro/commits/[email protected]/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 5.15.6
  dependency-type: direct:production
...

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

Author: dependabot[bot]

packages/docs/package.json

@@ -22,7 +22,7 @@
     "@beoe/rehype-penrose": "workspace:*",
     "@beoe/rehype-vizdom": "workspace:*",
     "@dagrejs/graphlib": "^2.2.4",
-    "astro": "5.5.5",
+    "astro": "5.15.6",
     "playwright": "^1.51.1",
     "sharp": "^0.33.5",
     "starlight-package-managers": "^0.10.0",