Remove 'ro.art.hiddenapi.warning' system property

Toasts/dialog have been removed, so this is now unused.

Test: m, phone boots
Change-Id: Ia0c443a2561f276514337365a7b7d991fd5183a8
diff --git a/core/main.mk b/core/main.mk
index 9bda2ad..65b74a0 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -221,13 +221,11 @@
 # Enable dynamic linker and hidden API developer warnings for
 # userdebug, eng and non-REL builds
 ifneq ($(TARGET_BUILD_VARIANT),user)
-  ADDITIONAL_BUILD_PROPERTIES += ro.bionic.ld.warning=1 \
-                                 ro.art.hiddenapi.warning=1
+  ADDITIONAL_BUILD_PROPERTIES += ro.bionic.ld.warning=1
 else
 # Enable it for user builds as long as they are not final.
 ifneq ($(PLATFORM_VERSION_CODENAME),REL)
-  ADDITIONAL_BUILD_PROPERTIES += ro.bionic.ld.warning=1 \
-                                 ro.art.hiddenapi.warning=1
+  ADDITIONAL_BUILD_PROPERTIES += ro.bionic.ld.warning=1
 endif
 endif