Remove unneeded webkit prefix in css

services/web/public/stylesheets/app/editor/pdf.less

@@ -1,8 +1,4 @@
 @stripe-width: 20px;
-@-webkit-keyframes pdf-toolbar-stripes {
-  from  { background-position: 0 0; }
-  to    { background-position: @stripe-width 0; }
-}
 @keyframes pdf-toolbar-stripes {
   from  { background-position: 0 0; }
   to    { background-position: @stripe-width 0; }