Remove calling dismissKeyguard from UserController in switch-user flow.

Since SysUI (KeyguardViewMediator) is now handling the keyguard
dismissal itself during the user switch and ignoring the request coming
from UserController, we need to remove calling the dismissKeyguard
during user switch from UserController.

Otherwise, it hits the 2 second timeout and increse the user switch
duration by that amount when switching from lockscreen to a passwordless
user.

This CL has no side effects other than fixing the 2 second regression in
user switch.

KeyguardViewMediator change = Ic8c2cc62ac0528762245b212ed0bf63969c86668

Bug: 368017647
Test: atest UserControllerTest
Flag: EXEMPT bugfix
Change-Id: Ida594891c2be4a31b171f6c062a9792bbd0464dc