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](ruby/json@v2.1.0...v2.3.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile.lock

@@ -236,7 +236,7 @@ GEM
       concurrent-ruby (~> 1.0)
     ice_nine (0.11.2)
     ipaddress (0.8.3)
-    json (2.1.0)
+    json (2.3.1)
     jwt (2.2.1)
     kgio (2.11.3)
     knapsack (1.14.0)