Remove obsoleted note in 1998/schnitzi/Makefile

As Landon had me reapply the fixes I had originally made the note about
invalid input very likely causing a crash (though I incorrectly put it
as it will crash absolutely) in the Makefile is no longer valid.

1998/schnitzi/Makefile

@@ -130,7 +130,6 @@ all: data ${TARGET}
 	supernova deep_magic magic charon pluto
 
 ${PROG}: ${PROG}.c
-	@echo "NOTE: this program will crash on invalid input."
 	${CC} ${CFLAGS} $< -o $@ ${LIBS}
 
 # alternative executable