build(deps): bump json from 2.19.5 to 2.21.2 in /site

Bumps [json](https://github.com/ruby/json) from 2.19.5 to 2.21.2.
- [Release notes](https://github.com/ruby/json/releases)
- [Changelog](https://github.com/ruby/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.19.5...v2.21.2)

---
updated-dependencies:
- dependency-name: json
  dependency-version: 2.21.2
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

site/Gemfile.lock

@@ -87,7 +87,7 @@ GEM
       sass-embedded (~> 1.75)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    json (2.19.5)
+    json (2.21.2)
     kramdown (2.5.1)
       rexml (>= 3.3.9)
     kramdown-parser-gfm (1.1.0)