Remove duplicate layout mobile_network_settings_container_v2

- MobileNetworkActivity can use settings_base_layout.xml as layout.
- MobileNetworkActivity need to use Theme.Settings.Home because
it requests Window.FEATURE_NO_TITLE. Otherwise MobileNetworkActivity
will show title defined in xml first then change to new title.

Fixes: 123794771
Test: rebuild, manual
Change-Id: I39ae25b6d335437ffddb2f1562e7a0347db97108