GridRichNode was removed in GridGain 6.0.3 to remove duplicity that existed between GridNode and GridRichNode APIs.
To get the same functionality as for GridRichNode, you now need to get a projection over a specific node, like so:
GridNode node = ...; // Get a single node.
GridProjection nodePrj = grid.forNode(node);
// Send a message to specific node.
nodePrj.send(...)