chore(deps): bump sharp and astro in /astro-site

Bumps [sharp](https://github.com/lovell/sharp) to 0.35.3 and updates ancestor dependency [astro](https://github.com/withastro/astro/tree/HEAD/packages/astro). These dependencies need to be updated together.


Updates `sharp` from 0.34.5 to 0.35.3
- [Release notes](https://github.com/lovell/sharp/releases)
- [Commits](lovell/sharp@v0.34.5...v0.35.3)

Updates `astro` from 6.1.8 to 7.1.3
- [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@7.1.3/packages/astro)

---
updated-dependencies:
- dependency-name: sharp
  dependency-version: 0.35.3
  dependency-type: indirect
- dependency-name: astro
  dependency-version: 7.1.3
  dependency-type: direct:production
...

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Author: dependabot[bot]