Restrict creation of secondary users TestDPC

Background
* Secondary users should be disabled
  when the device is an organization-owned
  managed profile device.
* This is because supporting secondary
  users would complicate the semantics of
  user restrictions.

Changes
* Remove 'Disallow add user' from list of
  user restrictions the profile owner of
  an organization-owned managed profile
  device can set on the parent profile.

Manual Testing Steps
* Provision an organization-owned managed
  profile device.
* Check WP TestDPC 'Set user restrictions
  on parent' and verify 'Disallow add user'
  is not present.

Bug: 155281701
Test: Manual testing
Change-Id: I4706cda0aa2b72c786daf08a03502406b3819cf8

Author: Alex Johnston

app/src/main/java/com/afwsamples/testdpc/policy/UserRestriction.java

@@ -221,8 +221,6 @@ public UserRestriction(String key, int titleResId) {
                     R.string.disallow_data_roaming),
             new UserRestriction(DISALLOW_DEBUGGING_FEATURES,
                     R.string.disallow_debugging_features),
-            new UserRestriction(DISALLOW_ADD_USER,
-                    R.string.disallow_add_user),
             new UserRestriction(DISALLOW_BLUETOOTH,
                     R.string.disallow_bluetooth),
             new UserRestriction(DISALLOW_BLUETOOTH_SHARING,