If it's grey out, users don't have the alternative way in that page to enable it. According to the UX design, we should hide it if it is needed.
Bug: 186776534
Test: make RunSettingsRoboTests -j52 ROBOTEST_FILTER=AccessibilityButtonLocationPreferenceControllerTest
Change-Id: If2f659da32345938e2930fde42365cd796571068