Removed layout_builder_blank from the option list

Closes #3445172

src/DisplayLayoutFormTrait.php

@@ -44,6 +44,7 @@ trait DisplayLayoutFormTrait {
     $layout_options = [];
 
     $layouts = $this->getLayoutPluginManager()->getDefinitions();
+    unset($layouts['layout_builder_blank']);
     foreach ($layouts as $key => $layout_definition) {
       // Create new layout option group.
       if (empty($key)) {