Fix the wrong link URL of 'doc-contrib-guide' for cleanup
Fix the wrong link URL of 'doc-contrib-guide' for cleanup

Since Queens update the link URL of 'Documentation Contributor Guide'
to distinguish this document from the new document aimed at all
new OpenStack contributors. So this patch correct the wrong url.
Refer to 'https://docs.openstack.org/releasenotes/openstack-manuals/queens'

Change-Id: I4d30d25db5f0b602dbad87f9ab714dd2ff8d8958

openstack/training-guides,openstack/training-guides