Remove Vm.resource_group method

Previously moved method was deleted by another PR but still
being added backed in here (incorrectly).  Test caught the issue.

app/models/manageiq/providers/azure/cloud_manager/vm_or_template_shared.rb

@@ -6,9 +6,4 @@ def provider_service(connection = nil)
     connection ||= ext_management_system.connect
     ::Azure::Armrest::VirtualMachineService.new(connection)
   end
-
-  # The resource group is stored as part of the uid_ems. This splits it out.
-  def resource_group
-    uid_ems.split('\\')[1]
-  end
 end