Fix help keyboard shortcut for relative URL setups

CHANGELOG

@@ -13,6 +13,7 @@ v 8.5.2
   - Fix sidebar overlapping content when screen width was below 1200px
   - Fix error 500 when commenting on a commit
   - Fix broken icons on installations with relative URL (Artem Sidorenko)
+  - Fix help keyboard shortcut on relative URL setups (Artem Sidorenko)
 
 v 8.5.1
   - Fix group projects styles

app/assets/javascripts/shortcuts.js.coffee

@@ -13,8 +13,10 @@ class @Shortcuts
     if $('#modal-shortcuts').length > 0
       $('#modal-shortcuts').modal('show')
     else
+      url = '/help/shortcuts'
+      url = gon.relative_url_root + url if gon.relative_url_root?
       $.ajax(
-        url: '/help/shortcuts',
+        url: url,
         dataType: 'script',
         success: (e) ->
           if location and location.length > 0