fix: shadow blocks with variable fields are not allowed to be deserialized from XML (#7802)

core/xml.ts

@@ -995,10 +995,7 @@ function domToBlockHeadless(
         throw TypeError('Shadow block not allowed non-shadow child.');
       }
     }
-    // Ensure this block doesn't have any variable inputs.
-    if (block.getVarModels().length) {
-      throw TypeError('Shadow blocks cannot have variable references.');
-    }
+
     block.setShadow(true);
   }
   return block;