Fix FLAG_HOME_PANEL_DREAM in public-staging.xml

This java constant was incorrectly qouted

Flag: android.service.controls.flags.home_panel_dream
Test: Running a yet to be uploaded change to finalize_res.py
Bug: 390120561
Change-Id: Ied1bf0c42506324ffddc2bb1ad2b7951e57a1a50