[util] Remove obsolete Makefile rule for util/prototester.c

util/prototester.c was removed in commit a6d1815 ("Obsolete for some
time now") back in 2006.

Signed-off-by: Marin Hannache <mareo@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/util/Makefile

 BLIB = ../bin/blib.a
 CFLAGS = -Os
 
-all : hijack prototester mucurses_test
+all : hijack mucurses_test
 
 hijack : hijack.c
 	$(CC) $(CFLAGS) $(EXTRA_CFLAGS) -Wall -lpcap -o $@ $<
 
-prototester.o : prototester.c
-	$(CC) $(CFLAGS) $(EXTRA_CFLAGS) -Wall -o $@ -c $< -idirafter ../include
-
-prototester : prototester.o $(BLIB)
-	$(CC) -o $@ $< -lc $(BLIB)
-
 mucurses_test.o : mucurses_test.c
 	$(CC) $(CFLAGS) $(EXTRA_CFLAGS) -Wall -o $@ -c $<
 
 	$(CC) -o $@ $< -lc $(BLIB)
 
 clean :
-	rm -f hijack prototester mucurses_test *.o
+	rm -f hijack mucurses_test *.o