Fix battery saver number format issue

 - The summary of battery saver scheduler use util to convert the number
   but saver sticky preference use another way to convert it, update
   them to use the same convert method

Bug: 250684701
Test: make SettingsRoboTests
Change-Id: I4f188a2e8e9d4810d187b870e331dc84f50b2b6f
2 files changed