test: correct error message for htlc error propagation test

lnd_test.go

@@ -1554,7 +1554,7 @@ func testHtlcErrorPropagation(net *networkHarness, t *harnessTest) {
 		t.Fatalf("payment should have been rejected due to wrong " +
 			"HTLC amount")
 	} else if !strings.Contains(err.Error(), "htlc value") {
-		t.Fatalf("payment should have failed due to unknown preimage, "+
+		t.Fatalf("payment should have failed due to wrong amount, "+
 			"instead failed due to: %v", err)
 	}