Use fork suggestion helper in blob view

app/views/projects/_fork_suggestion.html.haml

-- if current_user
-  .js-file-fork-suggestion-section.file-fork-suggestion.hidden
+.js-file-fork-suggestion-section.file-fork-suggestion.hidden
   %span.file-fork-suggestion-note
     You're not allowed to
     %span.js-file-fork-suggestion-section-action

app/views/projects/blob/_header.html.haml

@@ -20,5 +20,5 @@
       = download_blob_button(blob)
       = view_on_environment_button(@commit.sha, @path, @environment) if @environment
 
-= render 'projects/fork_suggestion'
+= render_fork_suggestion
 = render_if_exists 'projects/blob/header_file_locks', project: @project, path: @path