Run onWallpaperColorsChanged_changeLockWallpaper only when flag off

The test is no longer valid when the new customziation picker ui flag is
on. Thus we should only run when the flag is disablde.

Test: NA
Bug: 384058746
Bug: 372281743
Flag: com.android.systemui.shared.new_customization_picker_ui
Change-Id: I748cb7018883d1777d2bcf5e1d7cfee717662853