Remove Forced Taskbar Hidden accessibility announcement and forced accessibility focus

This cl also removes forced hidden annoucement and focus for Bubble Bar since they are annouced together.
we are keeping the tasksbar show annoucement and focus since it is only way to notify user of taskbar being shown on screen until we figure out proper solution with talkback team.

Test: Manual, Presubmit
Bug: 383928453
Flag: EXEMPT bugfix
Change-Id: I2c32ea393da2509af49e2fce795759a6903b0451