build(deps): bump json from 2.3.0 to 2.3.1 in /docs/v3

Bumps [json](https://github.com/flori/json) from 2.3.0 to 2.3.1.
- [Release notes](https://github.com/flori/json/releases)
- [Changelog](https://github.com/flori/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.3.0...v2.3.1)

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

Author: dependabot[bot]

docs/v3/Gemfile.lock

@@ -46,7 +46,7 @@ GEM
       uber (~> 0.0.14)
     http_parser.rb (0.6.0)
     i18n (0.7.0)
-    json (2.3.0)
+    json (2.3.1)
     kramdown (1.17.0)
     libv8 (7.3.492.27.1)
     listen (3.0.8)