Bump json from 2.0.2 to 2.3.0

Bumps [json](https://github.com/flori/json) from 2.0.2 to 2.3.0.
- [Release notes](https://github.com/flori/json/releases)
- [Changelog](https://github.com/flori/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.0.2...v2.3.0)

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

Gemfile.lock

@@ -20,7 +20,7 @@ GEM
       async (~> 1.8)
     colorize (0.8.1)
     console (1.8.2)
-    json (2.0.2)
+    json (2.3.0)
     nio4r (2.5.2)
     protocol-hpack (1.4.2)
     protocol-http (0.15.1)