NuCivic/nucivic-internal#35 Fix typo in token name

NuCivic/nucivic-internal#35

### Acepting test
Run:
```bash
drush fr open_data_schema_map_dkan
```
Then if you go to/admin/config/services/odsm/edit/ckan_package_show you should see '[node:url:args:last]' instead of '[node:url:arg:last]'