[#70443650] Core::OrgVdcNetwork#vcloud_attributes response has changed

The response from OrgVdcNetwork#vcloud_attributes has changed in vcloud-core, as a result of fixing the get_network deprecation.

See https://github.com/alphagov/vcloud-core/pull/45 for details on the deprecation fix.

Once the new vcloud-core version is released as a Gem, the vcloud-net_launcher.gemspec should be updated to reflect the new vcloud-core version.