Use empty text for displayname loading state rather than a SizedBox.shrink to help with jumping messages

lib/widgets/chat_page/lazy_loading/message_displayname.dart

@@ -23,6 +23,6 @@ class MessageDisplayname extends ConsumerWidget {
           style: style,
           overflow: TextOverflow.ellipsis,
         ),
-        loading: SizedBox.shrink,
+        loading: () => Text(""),
       );
 }