ENGCOM-962: [Forwardport] Fix faulty admin spinner animation #14182

Author: Stanislav Idolov

app/design/adminhtml/Magento/backend/web/css/source/variables/_spinner.less

@@ -26,4 +26,4 @@
 @spinner-rotate-step: 45;
 
 //  One step in degree
-@spinner-delay: .9;
+@spinner-delay: .9s;