adding fields display message in innerHtml

[orthagh]

Using API to add fields, we have some messages displayed in the response:

**$ curl -X POST \
http://localhost/glpi/9.3-git/apirest.php/PluginFieldsField \
  -H 'Cache-Control: no-cache' \
  -H 'Content-Type: application/json' \
  -H 'Session-Token: njf99u23ddkp0qgrpap3podo3h' \
  -d ' {"input": {"default_value": "0", "is_active": 1, "label": "test_api", "plugin_fields_containers_id": 10, "type": "text"}}'
<script type='text/javascript'>document.getElementById('').innerHTML="<p class='center'>Changement de la structure de la base de données - glpi_plugin_fields_computertest1s (0 seconde)</p>";</script>
<script type='text/javascript'>document.getElementById('').innerHTML="<p class='center'>Changement de la structure de la base de données - glpi_plugin_fields_tickettest1s (0 seconde)</p>";</script>
{"id":21,"message":"Élément ajouté : testapifield2"}%