Remove unneeded PRODUCT_RUNTIMES.

Bug: 18465297
Change-Id: I16b53e6e1b9e7bdb3fa7168f19bec82a30f3850a
diff --git a/ranchu_arm64.mk b/ranchu_arm64.mk
index e9425d7..ad252ee 100644
--- a/ranchu_arm64.mk
+++ b/ranchu_arm64.mk
@@ -18,8 +18,6 @@
 $(call inherit-product, $(SRC_TARGET_DIR)/product/aosp_base_telephony.mk)
 $(call inherit-product, $(SRC_TARGET_DIR)/board/generic_arm64/device.mk)
 
-PRODUCT_RUNTIMES := runtime_libart_default
-
 PRODUCT_NAME := ranchu_arm64
 # Use the same BoardConfig as generic_arm64.
 PRODUCT_DEVICE := generic_arm64