Revert "Fix a redundant assignRelativeLayerForIme case"

This reverts commit f5b13525.

Reason for revert: b/225028378#comment10

Fix: 225028378
Bug: 219774897
Test: manual as issue steps:
  1) Open a WhatsApp conversation
  2) Now open the keyboard and try to attach something
  3) Expect the attachment menu should be visible on top of the IME
Change-Id: I5770e03bc1f0834384ffab8591b1641be6bff4f2