Fix typo in CI settings

[ci skip]

app/views/admin/application_settings/_form.html.haml

@@ -149,7 +149,7 @@
         .checkbox
           = f.label :shared_runners_enabled do
             = f.check_box :shared_runners_enabled
-            Enable shared runners for a new projects
+            Enable shared runners for new projects
 
     .form-group
       = f.label :max_artifacts_size, 'Maximum artifacts size (MB)', class: 'control-label col-sm-2'