lnwallet test: update test to new error message

lnwallet/interface_test.go

@@ -581,7 +581,7 @@ func testReservationInitiatorBalanceBelowDustCancel(miner *rpctest.Harness,
 		t.Fatalf("initialization should have failed due to " +
 			"insufficient local amount")
 
-	case !strings.Contains(err.Error(), "local output is too small"):
+	case !strings.Contains(err.Error(), "Funder balance too small"):
 		t.Fatalf("incorrect error: %v", err)
 	}
 }