[Docs Site] Bump astro from 5.4.1 to 5.5.4 (#21054)

* [Docs Site] Bump astro from 5.4.1 to 5.5.4

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 5.4.1 to 5.5.4.
- [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/[email protected]/packages/astro)

---
updated-dependencies:
- dependency-name: astro
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

* update @astrojs/mdx

---------

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

Author: dependabot[bot]