change error message (#5972)

features/RestApi.feature

www/api/class/centreon_administration_aclgroup.class.php

www/api/class/centreon_administration_widget.class.php

www/api/class/centreon_configuration_command.class.php

www/api/class/centreon_configuration_contact.class.php

www/api/class/centreon_configuration_contactgroup.class.php

www/api/class/centreon_configuration_graphcurve.class.php

www/api/class/centreon_configuration_graphtemplate.class.php

www/api/class/centreon_configuration_host.class.php

www/api/class/centreon_configuration_hostcategory.class.php

www/api/class/centreon_configuration_hostgroup.class.php

www/api/class/centreon_configuration_hosttemplate.class.php

www/api/class/centreon_configuration_manufacturer.class.php

www/api/class/centreon_configuration_meta.class.php

www/api/class/centreon_configuration_objects.class.php

www/api/class/centreon_configuration_poller.class.php

www/api/class/centreon_configuration_service.class.php

...pi/class/centreon_configuration_servicecategory.class.php

www/api/class/centreon_configuration_servicegroup.class.php

...pi/class/centreon_configuration_servicetemplate.class.php