Remove leftover DO/PO check in isPackageSuspended

We already check if the caller is a DO, PO, or a delegate in
enforceCanManageScope, the additional call to
getActiveAdminForCallerLocked makes this function inaccessible to
delegate applications and was removed.

Test: cts-tradefed run cts-dev --module CtsDevicePolicyManagerTestCases --test com.android.cts.devicepolicy.MixedDeviceOwnerTest#testDelegation
Change-Id: I5df0f19a017a3b6e130329940c79b12cbb95ec9e