Expose Context#PAC_PROXY_SERVICE as module lib API

Bug: 183938000
Test: make update-api
Change-Id: I4341e177b61df0311f0a3234f8814a0ae2cf9a1b

core/api/module-lib-current.txt

@@ -61,6 +61,7 @@ package android.content {
 
   public abstract class Context {
     method @NonNull public android.os.UserHandle getUser();
+    field public static final String PAC_PROXY_SERVICE = "pac_proxy";
     field public static final String TEST_NETWORK_SERVICE = "test_network";
   }
 

core/java/android/content/Context.java

@@ -4165,6 +4165,7 @@ public abstract class Context {
      * @see android.net.PacProxyManager
      * @hide
      */
+    @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
     public static final String PAC_PROXY_SERVICE = "pac_proxy";
 
     /**