trivial: Generate '{project}-doc' roles, not '{project}-doc-link'

The latter are overly verbose, while the former have a natural synergy
with the 'doc' role provided by Sphinx.

Change-Id: Ib2fd91c1115270d3eb7d8197efdf4b5e8a7316a9

doc/source/index.rst

@@ -142,7 +142,7 @@ Using the theme
     ('index', '[Output_filename].tex', u'[Title]',
      u'OpenStack contributors', 'manual'),
     ]
- 
+
     latex_engine = 'xelatex'
 
 External Link Helper
@@ -168,7 +168,7 @@ Then in the documentation source, link to a target using syntax like:
 
 .. code-block:: rst
 
-   :horizon-doc-link:`Launching Instances with Horizon <user/launch-instances.html>`
+   :horizon-doc:`Launching Instances with Horizon <user/launch-instances.html>`
 
 
 Demonstration example

openstackdocstheme/__init__.py

@@ -164,7 +164,7 @@ def setup_link_roles(app):
     for project_name in app.config.openstack_projects:
         url = 'https://docs.openstack.org/{}/{}/%s'.format(
             project_name, series)
-        role_name = '{}-doc-link'.format(project_name)
+        role_name = '{}-doc'.format(project_name)
         logger.info('adding role %s to link to %s', role_name, url)
         app.add_role(role_name, extlinks.make_link_role(url, project_name))