Remove todo from PrivateSpaceMaitainer code

This change removes the TODO comment that was tracking to move over to
Biometric intent KeyguardManager.createConfirmDeviceCredentialIntent.
The hidden KeyguardManager.createConfirmDeviceCredentialIntent is being
used by various frameworks clients and is still avialable for use in settings.

Bug: 304796434
Test: Manual
Flag: EXEMPT removing todo
Change-Id: I5566d56e743e88afbcca0c4167c8a797e41b1a97