fix(gossip): return after sending NACK on private data store failure (#5422)

When StorePvtData fails inside privateDataMessage, a NACK is sent via
msg.Ack(err) but the function continues executing due to a missing return
statement. This causes two problems:

1. msg.Ack(nil) is called unconditionally right after, sending a false
   success ACK to the sender even though the storage failed.
2. The debug log "Private data for collection X has been stored" is
   printed even when the data was not actually stored, which is misleading
   for operators trying to diagnose private data issues.

Adding an explicit return after the NACK ensures the function exits on
error and only reaches msg.Ack(nil) and the success log on the happy path.

Signed-off-by: Shridhar Panigrahi <sridharpanigrahi2006@gmail.com>

Author: veyron-kairo

gossip/state/state.go

@@ -364,6 +364,7 @@ func (s *GossipStateProviderImpl) privateDataMessage(msg protoext.ReceivedMessag
 	if err := s.ledger.StorePvtData(txID, txPvtRwSetWithConfig, pvtDataMsg.Payload.PrivateSimHeight); err != nil {
 		s.logger.Errorf("Wasn't able to persist private data for collection %s, due to %s", collectionName, err)
 		msg.Ack(err) // Sending NACK to indicate failure of storing collection
+		return
 	}
 
 	msg.Ack(nil)