Remove unused cruft

Author: cpq

step-7-webserver/nucleo-f429zi/Makefile

@@ -17,7 +17,7 @@ firmware.elf: $(SOURCES)
 	arm-none-eabi-gcc $(SOURCES) $(CFLAGS) $(LDFLAGS) -o $@
 
 firmware.bin: firmware.elf
-	$(DOCKER) arm-none-eabi-objcopy -O binary $< $@
+	arm-none-eabi-objcopy -O binary $< $@
 
 flash: firmware.bin
 	st-flash --reset write firmware.bin 0x8000000