Removing checked state description text for accessibility from some widgets.

1. The framework was appending some text to convey the state of a
   a CheckedTextView or a RadioButton or a ToggleButton or a Switch
   but the checked property already conveys that information. It is
   responsibility of the screen reader developer to append the state
   text based on the checked property. This change is requested by a
   few screen reader developers.

bug:5951683

Change-Id: Ieba6797770201155c48e37147ae375dfcb5238aa