Enable group child bg fix when redesign flag is on

The child background also causes issues for the redesign, so let's enable this fix even if the transparency flag is off.

Fix: 398804267
Bug: 378660052
Test: manually tested that the icon no longer gets cut off
Flag: android.app.notifications_redesign_templates
Change-Id: Ia4b78456a79becb9dbcef17dd1fafb126cbb9d68