Fix 1986/marshall/Makefile about compilers

I got the entry to work with clang quite a while back but I never
removed the comment saying that the entry might have problems with some
compilers. I suppose some might still but clang is pretty strict so it
probably is okay.

1986/marshall/Makefile

@@ -130,7 +130,6 @@ all: data ${TARGET}
 	supernova deep_magic magic charon pluto
 
 ${PROG}: ${PROG}.c
-	@echo "NOTE: This entry uses non-standard args to main() that do not work with modern compilers."
 	${CC} ${CFLAGS} $< -o $@ ${LIBS}
 
 # alternative executable