x86: image: drop unneeded grub call

It appears there isn't any Image/Build/grub/* define so this step looks
redundant.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

target/linux/x86/image/Makefile

@@ -93,7 +93,6 @@ ifneq ($(CONFIG_GRUB_IMAGES),)
 		-d "$(KDIR)/grub2" \
 		-r "hd0,msdos1" \
 		"$(BIN_DIR)/$(IMG_PREFIX)-combined-$(1).img"
-	$(call Image/Build/grub/$(1))
   endef
 endif