Documentation fix: Permission grant opt-out

The documentation for EXTRA_PROVISIONING_PERMISSION_GRANT_OPT_OUT says
it should be used ACTION_PROVISION_MANAGED_DEVICE. However, that is
deprecated since it's no longer needed (and there's another way to
provision a fully-managed device).

Remove reference to the deprecated constant and simply mention device
owner provisioning.

Bug: 182180699
Test: That it compiles.
Change-Id: I8681c09fb9fa008f0e2ccf62c5dad8d37cd1b843