Remove onToggleSoftInput

As CL[1] removed InputMethodService#onToggleSoftInput since framework
side changed internal protocal to simplify the toggle logic without
this method callback.

Also remove ClientCallbackImpl#onToggleSoftInput for
MultiClientInputMethod sample app part to sync this change.

[1]: I390dc029e7bcc30c200926a9bfbbbd0268a1f714

Bug: 182071625
Test: build MultiClientInputMethod
Change-Id: I25568d9d0a963562fdc1d4a021f7016689b9ca54
1 file changed