Revert "use ApplicationName::useFlatBackground at some other places to fix rendering."
Revert "use ApplicationName::useFlatBackground at some other places to fix rendering."

This reverts commit 1e5917d15ccfae999cde25fcb72059772df27fdc.

blue-shell/carbon-gtk,blueshell-next/carbon-gtk,blueshell-next/carbon-gtk,blue-shell/carbon-gtk,KDE/oxygen-gtk,KDE/oxygen-gtk