Fix fromBundle() for TimeDifference with zeroElapsedRealtime

This method was not adjusted when adding support for elapsed-realtime-based TimeDifference. Oops.

Fixes: 436820663
Test: atest NotificationMetricStyleTest
Flag: android.app.api_metric_style
Change-Id: I95e4323032c16d8163b2fe8b23c855b2cb58ecab