Bump json from 2.2.0 to 2.3.1

Bumps [json](https://github.com/flori/json) from 2.2.0 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@v2.2.0...v2.3.1)

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

Author: dependabot[bot]

Gemfile.lock

@@ -56,7 +56,7 @@ GEM
     httpclient (2.8.3)
     i18n (0.9.5)
       concurrent-ruby (~> 1.0)
-    json (2.2.0)
+    json (2.3.1)
     minitest (5.13.0)
     molinillo (0.6.6)
     nanaimo (0.2.6)