Modify LockScreenPolicyFragment in TestDPC

* Introduced new logic that allows the profile owner of an
  organization-owned device (COPE PO) to set the restriction
  KEYGUARD_DISABLE_SECURE_NOTIFICATIONS on the parent profile.

Bug: 149007069
Test: Manual testing with TestDPC
Change-Id: I542471368d981ca0ba9b69e0f9250269798c6f21

Author: acjohnstong

app/src/main/java/com/afwsamples/testdpc/policy/keyguard/LockScreenPolicyFragment.java

@@ -80,7 +80,6 @@ abstract static class Keys {
 
         static final Set<String> NOT_APPLICABLE_TO_PARENT
                 = new HashSet<>(Arrays.asList(new String[] {
-            KEYGUARD_DISABLE_SECURE_NOTIFICATIONS,
             KEYGUARD_DISABLE_UNREDACTED_NOTIFICATIONS,
         }));
     }

app/src/main/res/xml/lock_screen_preferences.xml

@@ -75,7 +75,6 @@
         <com.afwsamples.testdpc.common.preference.DpcSwitchPreference
             android:key="keyguard_disable_secure_notifications"
             android:title="@string/keyguard_disable_secure_notifications"
-            testdpc:admin="deviceOwner"
             testdpc:minSdkVersion="L" />
         <com.afwsamples.testdpc.common.preference.DpcSwitchPreference
             android:key="keyguard_disable_unredacted_notifications"