fix typo in contrib docs
fix typo in contrib docs

Change-Id: Iae9aa84f48092b1c0d19d7271f049a9ff786996f

nelsnelson/stevedore,citrix-openstack-build/stevedore,openstack/stevedore,mandeepdhami/stevedore,citrix-openstack-build/stevedore,JioCloud/stevedore,varunarya10/stevedore,nelsnelson/stevedore,JioCloud/stevedore,varunarya10/stevedore,mandeepdhami/stevedore