Update battery settings remaining time format

 - Update the remaining time format to align with status bar
 - Remove unused test case since no more less than 7 or 15 remaining time
   case for battery settings
 screenshots:
   https://screenshot.googleplex.com/8jPYPj7yznGFU4b.png
   https://screenshot.googleplex.com/5GYXA2tusSUVmVQ.png
   https://screenshot.googleplex.com/3EnB3ejAxAzP28q.png
   https://screenshot.googleplex.com/5jeUxwBEyHotf9d.png

Bug: 281685505
Test: make SettingsLibRoboTests
Change-Id: If33e1828582845f78d8ef666c2b74ab5bba22357