Remove IMMS#MSG_UNBIND_INPUT

This CL inlines

  InputMethodManagerService#MSG_UNBIND_INPUT

handler as it has always been executed from the calling thread.

There should be no observable behavior change.

Bug: 215609403
Test: presubmit
Change-Id: Ic0bc0768bf6d42b84c2e36353c822f748508e838
1 file changed