Revert "Add TaskbarModeSwitchRule to test both transient/persistent taskbar."

This reverts commit d5a6b5f6.

Reason for revert: Breaks tests due to "SharedPreferences in credential encrypted storage are not available until after user is unlocked"

Bug: 258256906
Change-Id: I1de69249685f9d2e71183357cf3eda8d443c7d97