Remove all_product_makefiles

It was unused, along with all_product_configs.

Bug: 228518445
Test: Presubmits
Change-Id: Ibd105241581f8b03254b8fee382d916ea3a98890
diff --git a/core/product_config.mk b/core/product_config.mk
index 35f018d..540289a 100644
--- a/core/product_config.mk
+++ b/core/product_config.mk
@@ -210,7 +210,6 @@
 # Dedup, extract product names, etc.
 product_paths := $(sort $(product_paths))
 all_named_products := $(sort $(call _first,$(product_paths),:))
-all_product_makefiles := $(sort $(call _second,$(product_paths),:))
 current_product_makefile := $(call _second,$(filter $(TARGET_PRODUCT):%,$(product_paths)),:)
 COMMON_LUNCH_CHOICES := $(sort $(common_lunch_choices))
 
@@ -273,8 +272,6 @@
 ############################################################################
 
 current_product_makefile :=
-all_product_makefiles :=
-all_product_configs :=
 
 #############################################################################
 # Quick check and assign default values