Remove the legacy mechanism to auto add an a11y shortcut capable tile

With the introduction of the a11y qs shortcut option in the a11y
settings page, for a11y features that has the a11y shortcut toggle, we
use different mechanism to auto add the tile. We no longer need the
legacy mechanism to auto add an a11y shortcut capable tile.

Bug: 330628129
Test: Manually turn on the a11y feature won't automatically add the tile
in QS Panel. Manually turn on the a11y feature's qs shortcut option will
automatically add the tile in the QS Panel.
Test: atest ReduceBrightColorsAutoAddableTest

Flag: ACONFIG android.view.accessibility.a11y_qs_shortcut TRUNKFOOD FULL
Flag: NA EXEMPT not able to feature flag config.xml change
Change-Id: Ie048f539bd82e62250b3adf46b53b8e59dd4794c