Update net-mobile.page (Mobile Broadband) for Quick Settings in GNOME 43
The <gui>Mobile Broadband</gui> section of the menu will expand.
is likely not valid anymore. Cannot test because that machine has no SIM card hardware slot. Also remove the <gui>
markup here for consistency, per #133 (closed).
See cd521453 and a92d6f46 for very similar examples of what needs to be done.