chore(deps): bump prismjs in /packages/docsify-server-renderer (#1332)

Bumps [prismjs](https://github.com/PrismJS/prism) from 1.19.0 to 1.21.0. - [Release notes](https://github.com/PrismJS/prism/releases) - [Changelog](https://github.com/PrismJS/prism/blob/master/CHANGELOG.md) - [Commits](PrismJS/prism@v1.19.0...v1.21.0) Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]