Add flag com.android.cellbroadcastreceiver.flags.enable_cellbroadcast_map_viewer to trunk_staging.

This change was automatically created by advancing the Gantry workflow at:
https://releasetracker.partner.android.com/changes/dn3b116000001?build_unique_id=com.android.cellbroadcastreceiver.flags.enable_cellbroadcast_map_viewer-platform
Do not edit this file manually or revert this change - use the Gantry workflow to manage the state of this flag.

Bug: 410738387
Flag: com.android.cellbroadcastreceiver.flags.enable_cellbroadcast_map_viewer
Ignore-AOSP-First: Flag change added internally for future AOSP release
Change-Id: Idbc900a5c2ad8263ca565e23a06b91aa75a9c4c1