[BC25 Dual Shade] Fix hover background for QS Edit back button

This change replaces the Modifier.drawBehind with
IconButtonDefaults.iconButtonColors to properly set the
container and content colors.

Bug: 429237574
Flag: com.android.systemui.qs_ui_refactor_compose_fragment
Test: UI change only. Existing unit tests still pass.
Change-Id: If53a20c65f10d5827b818c1311bdbed2c6a3ec58