Disable hover view cache in handwriting initiator

The handwriting initiator can cache the hover view so that subsequent
hover events can check whether they are within the cached hover view's
handwriting bounds to decide whether to continue showing the handwriting
hover icon. However this behavior is no longer correct since the the
hover event may be within the cached hover view's handwriting bounds,
but closer to another tracked view which doesn't support handwriting, in
which case the hover icon should not be shown. So the caching is
disabled to achieve the correct behaviour.

A performance investigation showed that caching did not speed up hover
event processing, so disabling it doesn't cause any regression.

Bug: 297962571
Test: tested manually

Change-Id: Ie42c5459655099bf4c718edc639e0a1f1dc50242