Remove duplicated search index data of "Live Caption"

root cause:
 - SI workaround to help AiAi index "Live Caption"
 - Accessibility add Live Caption in Android Q
 - Settings will enable dynamic index injected preference after Android R.

solution:
 - SI should not add raw data after Android R.
 - Accessibility should not index this preference.

Bug: 153713572
Test: rototest & manual
Change-Id: Icdc66d0d8ba7ebb09ad5a22a6347047955cf1a2d