Disable landscape mode for picker

This CL aims at disabling landscape mode for picker2 activity.
Landscape mode is currently not supported for picker and therefore
setting this flag helps to disable rotation to landscape mode.

Bug: 391986843
Flag: com.android.systemui.shared.new_customization_picker_ui
Test: Tested by building & installing picker on local and checking if
landscape rotation is happening

Change-Id: I155e3ac5f196c043555576b5efc691f415316afe