[battery] remove unnecessary testing for shade header

The new battery icon + estimate text doesn't expose levels the same way,
so we don't need these tests.

Test: ShadeHeaderControllerTest
Bug: 391606042
Flag: com.android.settingslib.flags.new_status_bar_icons
Change-Id: Iab7e2633ddb123f4c3a730ca8c0273a3abf22b02