chore: revert createdAt comparator

Author: xsahil03x

packages/stream_chat/lib/src/client/channel.dart

@@ -2951,13 +2951,8 @@ class ChannelClientState {
     );
   }
 
-  int _sortByCreatedAt(Message a, Message b) {
-    if (a.remoteCreatedAt != null && b.remoteCreatedAt != null) {
-      return a.remoteCreatedAt!.compareTo(b.remoteCreatedAt!);
-    }
-
-    return a.createdAt.compareTo(b.createdAt);
-  }
+  int _sortByCreatedAt(Message a, Message b) =>
+      a.createdAt.compareTo(b.createdAt);
 
   /// The channel state related to this client.
   ChannelState get _channelState => _channelStateController.value;