Remove x-json mime_type, rename to json_mime_types.

config/initializers/mime_types.rb

@@ -13,11 +13,10 @@ Mime::Type.register "video/mp4",  :mp4, [], [:m4v, :mov]
 Mime::Type.register "video/webm", :webm
 Mime::Type.register "video/ogg",  :ogv
-lfs_mime_types = %w(
+json_mime_types = %w(
   application/vnd.git-lfs+json
-  text/x-json
   application/json
 )
 Mime::Type.unregister :json
-Mime::Type.register 'application/json', :json, lfs_mime_types
+Mime::Type.register 'application/json', :json, json_mime_types