Unify use of can_current_user_push_code Presenter

app/views/projects/buttons/_koding.html.haml

-- if koding_enabled? && current_user && @repository.koding_yml && @project.user_can_push_to_branch?(current_user, @project.default_branch)
+- if koding_enabled? && current_user && @repository.koding_yml && @project.can_current_user_push_code?
   = link_to koding_project_url(@project), class: 'btn project-action-button inline', target: '_blank', rel: 'noopener noreferrer' do
     _('Run in IDE (Koding)')

app/views/projects/empty.html.haml

@@ -11,7 +11,7 @@
     %h4
       = _('The repository for this project is empty')
 
-    - if can?(current_user, :push_code, @project)
+    - if @project.can_current_user_push_code?
       %p
         - link_to_cli = link_to _('command line instructions'), '#repo-command-line-instructions'
         = _('If you already have files you can push them using the %{link_to_cli} below.').html_safe % { link_to_cli: link_to_cli }