Bump json from 2.1.0 to 2.5.1

Bumps [json](https://github.com/flori/json) from 2.1.0 to 2.5.1.
- [Release notes](https://github.com/flori/json/releases)
- [Changelog](https://github.com/flori/json/blob/master/CHANGES.md)
- [Commits](ruby/json@v2.1.0...v2.5.1)

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

Author: dependabot[bot]

Gemfile.lock

@@ -62,7 +62,7 @@ GEM
     i18n (1.8.9)
       concurrent-ruby (~> 1.0)
     ice_nine (0.11.2)
-    json (2.1.0)
+    json (2.5.1)
     method_source (0.8.2)
     minitest (5.14.4)
     parallel (1.20.1)