use g_format_size instead of g_format_size_for_display
use g_format_size instead of g_format_size_for_display

The latter has been deprecated in GLib 2.31 but g_format_size() has been added
in 2.30 so we can already use it without bumping the dep.

Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets