Remove verity.mk, verity_key, PRODUCT_VERITY_SIGNING_KEY

verity.mk is used to set the related variable for VB 1.0 support, but
we already removed VB 1.0. This change removes the unused code. We also
remove and block PRODUCT_VERITY_SIGNING_KEY in this change.

Bug: 241044073
Test: atest under build/make
Change-Id: Ifbcde7da27a931ef3b9d746b1c5a279d88c0ec85
diff --git a/core/config.mk b/core/config.mk
index ad4491c..181bdcf 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -164,6 +164,7 @@
 $(KATI_obsolete_var PRODUCT_SUPPORTS_VERITY,VB 1.0 and related variables are no longer supported)
 $(KATI_obsolete_var PRODUCT_SUPPORTS_VERITY_FEC,VB 1.0 and related variables are no longer supported)
 $(KATI_obsolete_var PRODUCT_SUPPORTS_BOOT_SIGNER,VB 1.0 and related variables are no longer supported)
+$(KATI_obsolete_var PRODUCT_VERITY_SIGNING_KEY,VB 1.0 and related variables are no longer supported)
 # Used to force goals to build.  Only use for conditionally defined goals.
 .PHONY: FORCE
 FORCE: