Adjust docs+venv tox environments requirements/dependencies
Adjust docs+venv tox environments requirements/dependencies

After a prior merge these sections are no longer valid and
need to be adjusted to reflect the removal of the optional
requirements file.

Change-Id: I2a93c8e55f0d692df6d074bd86ab1a5e6d11a03f

jimbobhickville/taskflow,pombredanne/taskflow-1,junneyang/taskflow,openstack/taskflow,pombredanne/taskflow-1,jimbobhickville/taskflow,openstack/taskflow,junneyang/taskflow