Removes usage of TARGET_NO_VENDOR_BOOT.

- true -> PRODUCT_BUILD_VENDOR_BOOT_IMAGE=false
- false -> (removed, uses default option which builds vendor-boot.img
            if BOARD_BOOT_HEADER_VERSION>=3)

Bug: 170423509
Test: Inspect build artifacts from treehugger.
Change-Id: Id16fbda7fdfc70d62db389d6efb5201cb0d6d4e3
diff --git a/core/config.mk b/core/config.mk
index 16fa988..e975214 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -157,6 +157,7 @@
 $(KATI_obsolete_var LOCAL_SANITIZE_BLACKLIST,Use LOCAL_SANITIZE_BLOCKLIST instead.)
 $(KATI_deprecated_var BOARD_PLAT_PUBLIC_SEPOLICY_DIR,Use SYSTEM_EXT_PUBLIC_SEPOLICY_DIRS instead.)
 $(KATI_deprecated_var BOARD_PLAT_PRIVATE_SEPOLICY_DIR,Use SYSTEM_EXT_PRIVATE_SEPOLICY_DIRS instead.)
+$(KATI_obsolete_var TARGET_NO_VENDOR_BOOT,Use PRODUCT_BUILD_VENDOR_BOOT_IMAGE instead)
 
 # Used to force goals to build.  Only use for conditionally defined goals.
 .PHONY: FORCE