Bump astro from 4.14.5 to 4.15.6

Bumps [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro) from 4.14.5 to 4.15.6.
- [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/astro@4.15.6/packages/astro)

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

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Author: dependabot[bot]