Stop hiding ReferencesHidden

There do not seem to be any ReferencesHidden issues
in this target. If there would be, we would not want
public APIs exposing hidden types anyway.

Test: make -j
Change-Id: I5bf57e080580b493a9f0281f0ee8ed3b539ae6d5

services/Android.bp

@@ -111,7 +111,6 @@ droidstubs {
         " --hide InternalClasses" + // com.android.* classes are okay in this interface
         // TODO: remove the --hide options below
         " --hide-package com.google.android.startop.iorap" +
-        " --hide ReferencesHidden" +
         " --hide DeprecationMismatch" +
         " --hide HiddenTypedefConstant",
     visibility: ["//visibility:private"],