chore(deps): bump immer, gatsby and gatsby-remark-highlight-code

Bumps [immer](https://github.com/immerjs/immer) to 9.0.21 and updates ancestor dependencies [immer](https://github.com/immerjs/immer), [gatsby](https://github.com/gatsbyjs/gatsby) and [gatsby-remark-highlight-code](https://github.com/deckgo/gatsby-remark-highlight-code). These dependencies need to be updated together.


Updates `immer` from 8.0.1 to 9.0.21
- [Release notes](https://github.com/immerjs/immer/releases)
- [Commits](immerjs/immer@v8.0.1...v9.0.21)

Updates `gatsby` from 4.0.2 to 4.25.8
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/compare/[email protected]@4.25.8)

Updates `gatsby-remark-highlight-code` from 3.0.1 to 3.3.0
- [Release notes](https://github.com/deckgo/gatsby-remark-highlight-code/releases)
- [Changelog](https://github.com/deckgo/gatsby-remark-highlight-code/blob/main/CHANGELOG.md)
- [Commits](deckgo/gatsby-remark-highlight-code@v3.0.1...v3.3.0)

---
updated-dependencies:
- dependency-name: immer
  dependency-type: indirect
- dependency-name: gatsby
  dependency-type: direct:production
- dependency-name: gatsby-remark-highlight-code
  dependency-type: direct:production
...

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