Update preview.html

Author: in-session

app/code/Magento/Ui/view/base/web/templates/grid/cells/thumbnail/preview.html

@@ -7,7 +7,7 @@
 
 <div class="thumbnail-preview" data-role="thumbnail-preview">
     <div class="thumbnail-preview-image-block">
-        <img class="thumbnail-preview-image" src="<%- src %>" alt="<%- alt %>" />
+        <img class="thumbnail-preview-image" src="<%- src %>" alt="<%- alt %>" loading="lazy"/>
     </div>
     <div class="thumbnail-preview-content">
         <a class="thumbnail-preview-link" href="<%- link %>"><%- linkText %></a>