Revert "Fix ContentObserver unregister issue"

This reverts commit 2df4e144a913b705c50bde929c75744b251967d9. 
It was causing failures in packages/apps/DocumentsUI tests

Bug: 63638102
Bug: 63154326
Change-Id: I51fb54f705f58f159f4fcc30bfed41ababcba950
1 file changed