Add label and children to semantics update (#6268)

We were missing these before.

packages/flutter/lib/src/rendering/semantics.dart

@@ -544,7 +544,9 @@ class SemanticsNode extends AbstractNode {
       flags: data.flags,
       actions: data.actions,
       rect: data.rect,
+      label: data.label,
       transform: data.transform?.storage ?? _kIdentityTransform,
+      children: children,
     );
     _dirty = false;
   }