Update Downloadable.php

Declare module namespace before template path

Author: mageprince

app/code/Magento/Downloadable/Block/Adminhtml/Catalog/Product/Edit/Tab/Downloadable.php

@@ -33,7 +33,7 @@ class Downloadable extends Widget implements TabInterface
     /**
      * @var string
      */
-    protected $_template = 'product/edit/downloadable.phtml';
+    protected $_template = 'Magento_Downloadable::product/edit/downloadable.phtml';
 
     /**
      * Accordion block id