Removes user icon tinting.

This fixes b/253637739 where the guest user icon color is incorrect in
both the status bar and quick settings action footer when the footer is
revealed.

The reason it was affecting status bar was because setting the tint
mutates the drawable that both components share.

Either way, removing this unnecessary tinting fixes the issue.

Fix: 253637739
Test: updated one unit test and manually verified that both the primary
user and the guest user look as expected in both the status bar and the
quick settings footer in both dark and light theme on a tablet

Change-Id: Ib7fba1c39dbdf5ea1c252d58b468c4c5f83ee5e8