small rst stylefix on subunit data upload spec
small rst stylefix on subunit data upload spec

While writing up the subunit upload spec, I went to grab the link
of the original spec off of github and realized that the data model
visualizations were nigh unreadable due to a lack of block literal
usage. This patch adds a block literal to restore readability.

Change-Id: Ie17d7b096300d5db706b948e8532b0380f42aaaf

stackforge/refstack,stackforge/refstack,openstack/refstack,stackforge/refstack,stackforge/refstack,openstack/refstack,openstack/refstack,openstack/refstack