Bump json from 2.1.0 to 2.3.1 (sass#462)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -60,7 +60,7 @@ GEM
     htmlcompressor (0.2.0)
     http_parser.rb (0.6.0)
     i18n (0.7.0)
-    json (2.1.0)
+    json (2.3.1)
     kramdown (1.17.0)
     libv8 (3.16.14.19)
     listen (3.0.8)