Workflow documentation is now in infra-manual

Replace URLs for workflow documentation to appropriate parts of the
OpenStack Project Infrastructure Manual.

Change-Id: Id09c9bdf8804c1ed90e49606e76ffbff1d96a7c2

Author: fungi

doc/source/index.rst

@@ -37,7 +37,7 @@ the openstack/python-openstackclient project using `Gerrit`_.
 
 .. _on OpenStack's Git server: https://git.openstack.org/cgit/openstack/python-openstackclient/tree
 .. _Launchpad: https://launchpad.net/python-openstackclient
-.. _Gerrit: http://wiki.openstack.org/GerritWorkflow
+.. _Gerrit: http://docs.openstack.org/infra/manual/developers.html#development-workflow
 
 Indices and Tables
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