Revert "Fix the logics in ImeFocusController#onPostWindowFocus"

This reverts commit a56779d1 [1].

Reason for revert:
Caused multiple test failures in CtsInputMethodTestCases

 [1]: I68bb95fc3cbfe1f5992ccf87694b34c3e52bb31f

Bug: 153612876
Fix: 154250671
Test: atest CtsInputMethodTestCases
Change-Id: Ibf6143f46ae18e41e8ecfa50f523216e7340adda