Skip depth and scrim if freeform tasks are visible

If freeform tasks are shown, skip applying depth effect and scrim
changes. These cause the background to flicker while showing freeform
tasks and for example showing the transient taskbar.

Bug: 263264985
Test: swipe up to show transient taskbar, observe launcher background
does not blur or flicker to black

Change-Id: I5b10d0f0c7065e903cb761488367c02d7e31d8b2