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] <[email protected]>

Author: dependabot[bot]

Gemfile.lock

@@ -33,7 +33,7 @@ GEM
     hiera (3.3.1)
     httparty (0.15.6)
       multi_xml (>= 0.5.2)
-    json (2.1.0)
+    json (2.5.1)
     json_pure (1.8.6)
     locale (2.1.2)
     method_source (0.8.2)