Update Android.mk for android.preference after removed from CtsTestStubs

bug: 17211776
Change-Id: Ia06ea21280f76cde5c1dce76443f3f71fd5ac473
diff --git a/tests/tests/preference/Android.mk b/tests/tests/preference/Android.mk
index 5860406..7534641 100644
--- a/tests/tests/preference/Android.mk
+++ b/tests/tests/preference/Android.mk
@@ -26,8 +26,6 @@
 
 LOCAL_PACKAGE_NAME := CtsPreferenceTestCases
 
-LOCAL_INSTRUMENTATION_FOR := CtsTestStubs
-
 LOCAL_SDK_VERSION := current
 
 include $(BUILD_CTS_PACKAGE)