Remove quicksearchbox from home window list

Previously Winscope considered only the `isVisible` property to determine if the window was visible or not. This failed in cases such as `com.google.android.googlequicksearchbox/android.app.ContextImpl` when launching apps, where `isVisible=true` and `alpha=0`

Bug: 181630910
Bug: 182720234
Test: atest FlickerTests WMShellFlickerTests
Change-Id: I75fab0c6de02e43265002986901353f8e230baa5