Add target blank to usage quota help link

app/views/projects/usage_quotas/index.html.haml

@@ -6,7 +6,7 @@
 .row
   .col-sm-12
     = s_('UsageQuota|Usage of project resources across the %{strong_start}%{project_name}%{strong_end} project').html_safe % { strong_start: '<strong>'.html_safe, strong_end: '</strong>'.html_safe, project_name: @project.name } + '.'
-    %a{ href: help_page_path('user/usage_quotas.md') }
+    %a{ href: help_page_path('user/usage_quotas.md'), target: '_blank', rel: 'noopener noreferrer' }
       = s_('UsageQuota|Learn more about usage quotas') + '.'
 
 .top-area.scrolling-tabs-container.inner-page-scroll-tabs