Bump json from 2.2.0 to 2.5.1 in /components/courses

Bumps [json](https://github.com/flori/json) from 2.2.0 to 2.5.1.
- [Release notes](https://github.com/flori/json/releases)
- [Changelog](https://github.com/flori/json/blob/master/CHANGES.md)
- [Commits](flori/json@v2.2.0...v2.5.1)

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

components/courses/Gemfile.lock

@@ -99,7 +99,7 @@ GEM
       rspec (>= 2.99.0, < 4.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
-    json (2.2.0)
+    json (2.5.1)
     kaminari (1.1.1)
       activesupport (>= 4.1.0)
       kaminari-actionview (= 1.1.1)
@@ -127,7 +127,9 @@ GEM
     marcel (0.3.3)
       mimemagic (~> 0.3.2)
     method_source (0.9.2)
-    mimemagic (0.3.3)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.1)
     mini_portile2 (2.4.0)
     minitest (5.11.3)