MAGETWO-33716: Moved js files

Author: Joan He

app/code/Magento/Email/view/adminhtml/templates/template/edit.phtml

@@ -57,7 +57,7 @@ require([
     "jquery",
     "tinymce",
     "mage/mage",
-    "Magento_Backend/variables"
+    "Magento_Variable/variables"
 ], function(jQuery, tinyMCE){
 
 //<![CDATA[