Remove redundant icons and temp controls from nav bar

- Remove assistant icon from nav bar (assistant widget now visible on
home screen)
- Remove tapping temperature views opens HVAC controls. HVAC controls
are accessible via the HVAC nav button

Bug: 169043149
Test: manual - built on flame_car
Change-Id: I6f437560bc9fd040d5a44a27902c9f579125bac9