Configuration Guide in cloudkitty - Correct typo

[Vincent Misson]

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [X] This doc is inaccurate in this way:
<==
openstack role add --project service --user cloudkitty admin
==>
openstack role add --project services --user cloudkitty admin

- [ ] This is a doc addition request.
- [ ] I have a fix to the document that I can paste below including example: input and output.

If you have a troubleshooting or support issue, use the following resources:

 - Ask OpenStack: http://ask.openstack.org
 - The mailing list: http://lists.openstack.org
 - IRC: 'openstack' channel on Freenode

-----------------------------------
Release: 7.0.1.dev43 on 2018-06-29 12:05
SHA: 041f212add80d0355d6345e28911f74d6d87410f
Source: https://git.openstack.org/cgit/openstack/cloudkitty/tree/doc/source/configuration/configuration.rst
URL: https://docs.openstack.org/cloudkitty/latest/configuration/configuration.html

[Pierre Riteau (priteau)]

The name of the project used by services is not necessarily the same across all deployments. It can be "service" or "services" depending on how you installed OpenStack.

There is a note about it on the page you referenced, since June 2017: https://review.opendev.org/#/c/464567/