build(deps): bump nextra from 3.3.1 to 4.2.13 in /docs

Bumps [nextra](https://github.com/shuding/nextra) from 3.3.1 to 4.2.13.
- [Release notes](https://github.com/shuding/nextra/releases)
- [Commits](https://github.com/shuding/nextra/compare/nextra@3.3.1...nextra@4.2.13)

---
updated-dependencies:
- dependency-name: nextra
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]