Revert "Camera VTS: Improve test for torch callback"

This reverts commit f415f561.

Current HAL assumes that no new setCallback() is called after the start
of camera provider. Having more than one callback listeners breaks that
implicit assumption. It may not be trivial for HAL to add support for
multiple callback listeners

Test: CameraAidlTest#setTorchMode passes
Bug: 251111588
Change-Id: Idd2a250dc325b1a1080c1fa6562507e563cf545c