Revert "Have WM use token info. from IMMS to determine IME target window"

This reverts commit daab8653.

IMMS is currently sending wrong target candidates, so we need to revert
this until we figure-out what is going on there :(

Bug: 31559891
Bug: 35903813
Test: DisplayContentTests
Change-Id: I5c5beff4bac1b0781fa6663b13ff0dfe83a7806b