Bump ckeditor from 4.2.4 to 4.3.0

This version solves a security issue:

https://ckeditor.com/cke4/release/CKEditor-4.11.0

Note this version adds a `ckeditor/samples` folder, which is
automatically added to the application's assets manifest even if we
remove all CKEditor references in our application. One of the files in
that folder makes ExecJS raise a syntax error, causing every page to
raise a 500 error.

config/initializers/ckeditor.rb

@@ -9,4 +9,5 @@ Ckeditor.setup do |config|
 
   config.assets_languages = Rails.application.config.i18n.available_locales.map { |l| l.to_s.downcase }
   config.assets_plugins = %w[copyformatting image link magicline scayt table tableselection wsc]
+  config.assets.reject! { |asset| asset =~ /\Ackeditor\/samples\// }
 end