Rename PRODUCT_USES_ART to PRODUCT_USES_DEFAULT_ART_CONFIG

It better describes what is meant to represent.

Test: m build
Change-Id: I942721cee2c7eaef625bf8c64aae32c1725705eb
diff --git a/core/product.mk b/core/product.mk
index 192d58c..3f52987 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -245,7 +245,7 @@
 _product_var_list += \
     PRODUCT_USE_PROFILE_FOR_BOOT_IMAGE \
     PRODUCT_DEX_PREOPT_BOOT_IMAGE_PROFILE_LOCATION \
-    PRODUCT_USES_ART \
+    PRODUCT_USES_DEFAULT_ART_CONFIG \
 
 _product_var_list += PRODUCT_SYSTEM_SERVER_COMPILER_FILTER
 # Per-module sanitizer configs