Cleanup of color contrast flag

This CL aims at cleanup of the color contrast flag since the flag has
been fully rolled out.

Bug: 409604482
Flag: EXEMPT removing com.android.settings.accessibility.enable_color_contrast_control
Test: Tested by building and running picker on local
Change-Id: I06d3e08cecca1dd5ac81697856dcd209cc308fde
1 file changed