routerrpc: default timeout_seconds to 60 in SendPaymentV2

If timeout_seconds is not set or is 0, the default value
of 60 seconds will be used.

Signed-off-by: Nishant Bansal <nishant.bansal.282003@gmail.com>

lnrpc/routerrpc/router_backend.go

@@ -878,11 +878,6 @@ func (r *RouterBackend) extractIntentFromSendRequest(
 		return nil, err
 	}
 
-	// Set payment attempt timeout.
-	if rpcPayReq.TimeoutSeconds == 0 {
-		return nil, errors.New("timeout_seconds must be specified")
-	}
-
 	customRecords := record.CustomSet(rpcPayReq.DestCustomRecords)
 	if err := customRecords.Validate(); err != nil {
 		return nil, err