Merge remote-tracking branch 'origin/MAGETWO-44561' into PR

Author: Volodymyr Zaets

app/code/Magento/ConfigurableProduct/view/adminhtml/templates/catalog/product/edit/super/config.phtml

@@ -36,7 +36,7 @@
             </div>
         </div>
     </div>
-    <fieldset class="fieldset">
+    <div class="fieldset">
         <?php echo $block->getChildHtml('matrix'); ?>
 
         <!-- Select Associated Product popup -->
@@ -53,7 +53,7 @@
         </div>
 
         <input type="hidden" name="affect_configurable_product_attributes" value="1" />
-    </fieldset>
+    </div>
 </div>
 <script>
 require([