Bump the dependabot group in /website with 2 updates

Bumps the dependabot group in /website with 2 updates: [@astrojs/starlight](https://github.com/withastro/starlight/tree/HEAD/packages/starlight) and [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro).


Updates `@astrojs/starlight` from 0.30.1 to 0.31.1
- [Release notes](https://github.com/withastro/starlight/releases)
- [Changelog](https://github.com/withastro/starlight/blob/main/packages/starlight/CHANGELOG.md)
- [Commits](https://github.com/withastro/starlight/commits/@astrojs/starlight@0.31.1/packages/starlight)

Updates `astro` from 5.1.0 to 5.1.7
- [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@5.1.7/packages/astro)

---
updated-dependencies:
- dependency-name: "@astrojs/starlight"
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: dependabot
- dependency-name: astro
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: dependabot
...

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