Use removeUserEvenWhenDisallowed for removing ephemeral user

- To bypass DISALLOW_REMOVE_USER check

Bug: 72437780
Test: cts-tradefed run singleCommand cts -m DevicePolicyManager --test com.android.cts.devicepolicy.DeviceOwnerTest#testCreateAndManageUser_StopEphemeralUser_DisallowRemoveUser
Change-Id: Ib07ccc4cdbd8da2c2b314da30479e10b9085b697