gio: Fix application of GNetworkMonitor:network-metered patch

The wrong patch from https://bugzilla.gnome.org/show_bug.cgi?id=750282
was applied, causing test failures due to not implementing the property
on GNetworkMonitorBase (plus some other omissions).

Fix that by reverting commit a80e7db1
and re-applying the correct patch over the top.

https://bugzilla.gnome.org/show_bug.cgi?id=750282