Remove docs from linters

The openstack-ansible-linters job runs the linters tox environment - and
the docs jobs runs the docs environment.

Remove the docs jobs from the linters environment, there's no need to
run the docs jobs in both linters and docs environment, it just wastes
testing resources.

Change-Id: Ie72970439c498f7c4ff274138544af0611376e87

tox.ini

@@ -91,12 +91,9 @@ commands =
 
 [testenv:linters]
 basepython = python3
-deps =
-    -r{toxinidir}/doc/requirements.txt
 commands =
     bash -c "{toxinidir}/tests/common/test-ansible-env-prep.sh"
     {[testenv:pep8]commands}
     {[testenv:bashate]commands}
     {[testenv:ansible-lint]commands}
     {[testenv:ansible-syntax]commands}
-    {[testenv:docs]commands}