Remove event listeners when touch session ends

Currently, the event listeners may still run after the touch session has
ended, which is causing NullPointerException to be thrown

Was able to reproduce this by forcing dreams to switch while swiping up
on the screen to bring up the bouncer.

Bug: 275659024
Test: atest DreamOverlayTouchMonitorTest
Change-Id: I2e47d16231e0f7297e4e7781325a6de9f8e8c948