Remove IMM#reportVirtualDisplayGeometry() again

This CL effectively reverts our previous CL [1], which re-introduced

  InputMethodManager#reportVirtualDisplayGeometry()

for certain form-factors.

Now that we no longer need this @hide API, let's remove this for
simplicity.

 [1]: I35b491da5a340844e17542d7a6198f8152bbeda3
      708c957f

Bug: 224424149
Bug: 256926300
Test: presubmit
Test: atest FrameworksInputMethodSystemServerTests:InputMethodManagerServiceWindowGainedFocusTest
Change-Id: Ic956c84e39ab24ef6cf946a32f1acb954d6eec38