patch 9.0.1648: result of syntax tests is hard to see

Problem:    Result of syntax tests is hard to see.
Solution:   List the failed tests.
diff --git a/runtime/syntax/Makefile b/runtime/syntax/Makefile
index 08bc824..a52c7d6 100644
--- a/runtime/syntax/Makefile
+++ b/runtime/syntax/Makefile
@@ -26,7 +26,7 @@
 	@echo "../$(VIMPROG)" > testdir/vimcmd
 	@echo "$(RUN_VIMTEST)" >> testdir/vimcmd
 	VIMRUNTIME=$(VIMRUNTIME) $(VIMPROG) --clean --not-a-term $(DEBUGLOG) -u testdir/runtest.vim
-	@tail -n 5 testdir/messages
+	@tail -n 6 testdir/messages
 
 
 clean testclean: