[aws] One line change to be able to delete AWS tag

I have know idea if that was intentional but with that action set the
  method does not delete tags.  Setting it to the DeleteTags action does.

lib/fog/compute/requests/aws/delete_tags.rb

@@ -26,7 +26,7 @@ module Fog
           params.merge!(AWS.indexed_param('Tag.%d.Key', tags.keys))
           params.merge!(AWS.indexed_param('Tag.%d.Value', tags.values))
           request({
-            'Action'            => 'CreateTags',
+            'Action'            => 'DeleteTags',
             :parser             => Fog::Parsers::AWS::Compute::Basic.new
           }.merge!(params))
         end