[shade] add stacked_mobile to the list of hidden icons

This makes sure that the stacked dual-SIM icon is also hidden in the
shade header just like the regular mobile icons are.

Test: manual
Bug: 402663625
Flag: com.android.settingslib.flags.new_status_bar_icons
Change-Id: I54ad74a89afeb5ed0e7488a5fd4ab20e8ff54e45