Bump json from 1.8.3 to 2.3.0

Bumps [json](https://github.com/flori/json) from 1.8.3 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@v1.8.3...v2.3.0)

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

Author: dependabot[bot]

Gemfile.lock

@@ -1,7 +1,7 @@
 GEM
   remote: http://rubygems.org/
   specs:
-    json (1.8.3)
+    json (2.3.0)
     minitest (5.8.4)
     rake (10.5.0)