Remove battery event time detection from StylusUpdater.

StylusManager battery listener now triggers whenever the
stylus battery becomes stale, so we no longer need to track
event time from the updater.

Bug: 270422546
Test: StylusDeviceUpdaterTest
Change-Id: I36f5dc132a95f7d4649cec2bda1d457edc1f64bd
2 files changed