Bump json from 2.1.0 to 2.3.1

Bumps [json](https://github.com/flori/json) from 2.1.0 to 2.3.1.
- [Release notes](https://github.com/flori/json/releases)
- [Changelog](https://github.com/flori/json/blob/master/CHANGES.md)
- [Commits](flori/json@v2.1.0...v2.3.1)

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

Gemfile.lock

@@ -32,7 +32,7 @@ GEM
     hashdiff (0.3.7)
     i18n (1.0.1)
       concurrent-ruby (~> 1.0)
-    json (2.1.0)
+    json (2.3.1)
     mini_portile2 (2.3.0)
     minitest (5.11.3)
     net-http-report (0.1.0)