Fix plugin icon with Redmine 3.4.x

Author: n-rodriguez

lib/redmine_git_hosting.rb

@@ -3,7 +3,7 @@
 
 ## Redmine Menus
 Redmine::MenuManager.map :admin_menu do |menu|
-  menu.push :redmine_git_hosting, { controller: 'settings', action: 'plugin', id: 'redmine_git_hosting' }, caption: :redmine_git_hosting
+  menu.push :redmine_git_hosting, { controller: 'settings', action: 'plugin', id: 'redmine_git_hosting' }, caption: :redmine_git_hosting, html: { class: 'icon' }
 end
 
 Redmine::MenuManager.map :top_menu do |menu|