Bump json from 1.7.6 to 1.8.6

Bumps [json](https://github.com/flori/json) from 1.7.6 to 1.8.6.
- [Release notes](https://github.com/flori/json/releases)
- [Changelog](https://github.com/flori/json/blob/master/CHANGES.md)
- [Commits](flori/json@v1.7.6...v1.8.6)

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

Gemfile.lock

@@ -41,7 +41,7 @@ GEM
     erubis (2.7.0)
     hike (1.2.3)
     i18n (0.6.5)
-    json (1.7.6)
+    json (1.8.6)
     mail (2.5.4)
       mime-types (~> 1.16)
       treetop (~> 1.4.8)