Bump json from 2.7.3 to 2.7.5 in /docs

Bumps [json](https://github.com/ruby/json) from 2.7.3 to 2.7.5.
- [Release notes](https://github.com/ruby/json/releases)
- [Changelog](https://github.com/ruby/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.7.3...v2.7.5)

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

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

Author: dependabot[bot]

docs/Gemfile.lock

@@ -65,7 +65,7 @@ GEM
       jekyll (>= 3.8, < 5.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    json (2.7.3)
+    json (2.7.5)
     kramdown (2.4.0)
       rexml
     kramdown-parser-gfm (1.1.0)