Bump json from 1.7.4 to 2.3.1 in /edx_specs

Bumps [json](https://github.com/flori/json) from 1.7.4 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@v1.7.4...v2.3.1)

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

Author: dependabot[bot]

edx_specs/Gemfile.lock

@@ -24,7 +24,7 @@ GEM
     ffi (1.1.5)
     http_parser.rb (0.5.3)
     i18n (0.6.0)
-    json (1.7.4)
+    json (2.3.1)
     launchy (2.1.1)
       addressable (~> 2.3)
     libwebsocket (0.1.5)