renderers.yaml: xrange() => six.range()

```
************* Module salt.renderers.yaml
salt/renderers/yaml.py:93: [W1613(xrange-builtin), _yaml_result_unicode_to_utf8] xrange built-in referenced
salt/renderers/yaml.py:96: [W1613(xrange-builtin), _yaml_result_unicode_to_utf8] xrange built-in referenced
```