Remove enabled flag fix_merged_content_change_event_v2

It has been enabled 6 month.

Bug: 277305460
Test: atest AccessibilityEventAndCacheTest
Flag: EXEMPT removing com.android.server.accessibility.fix_merged_content_change_event_v2
Change-Id: Icbc3e9dde072d10ec1800897cf0f95c63ee95913
2 files changed