bump dress_code dependencies

Change-Id: I9b0d0244cb0bfc79105cf268c3e29617b875f342
Reviewed-on: https://gerrit.instructure.com/92387
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Jenkins
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

Author: ccutrer

Gemfile.d/assets.rb

@@ -3,7 +3,7 @@
     gem 'colored', '1.2', require: false
     gem 'mustache', '1.0.3', require: false
     gem 'pygments.rb', '0.5.4', require: false
-      gem 'posix-spawn', '0.3.8', require: false
+      gem 'posix-spawn', '0.3.9', require: false
       gem 'yajl-ruby', '1.1.0', require: false
   gem 'fontcustom', '~> 1.3.3', require: false
 end