Bump astro from 5.15.3 to 5.15.4

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.15.3 to 5.15.4.
- [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/astro@5.15.4/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-version: 5.15.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -11,7 +11,7 @@
   },
   "dependencies": {
     "@astrojs/starlight": "0.36.2",
-    "astro": "5.15.3",
+    "astro": "5.15.4",
     "starlight-links-validator": "0.19.0"
   }
 }