Fix opendev-tox-docs job

With the upgrade of tox to a newer version we started to encounter
failures in the opendev-tox-docs job. It looks like the interpretation
of the variable skipdist changed.

A similar problem was solved in tempest repository by removing the
skipsdist option from tox [1]. It looks like a similar solution
works for python-tempestconf as well.

[1] https://review.opendev.org/c/openstack/tempest/+/868527

Depends-On: Ie5ea7f9305c7e7611f205d2e0703849bd6321a68
Change-Id: I9ee6570b72c10ea0466819008135ddebe891a445

.zuul.yaml

@@ -56,10 +56,7 @@
                 - octavia
             dependencies:
               - tripleo-ci-centos-9-content-provider
-        # temporarily marked to n-v, there is already a fix for this:
-        # https://review.opendev.org/c/openinfra/python-tempestconf/+/870548
-        - opendev-tox-docs:
-            voting: false
+        - opendev-tox-docs
     gate:
       jobs:
         - openstack-tox-py39
@@ -83,7 +80,7 @@
         #    vars: *standalone
         #    dependencies:
         #      - tripleo-ci-centos-9-content-provider
-        # - opendev-tox-docs
+        - opendev-tox-docs
     promote:
       jobs:
         - opendev-promote-docs

tox.ini

@@ -1,7 +1,6 @@
 [tox]
 minversion = 3.18.0
 envlist = py38,py37,py36,pypy,pep8
-skipsdist = True
 # this allows tox to infer the base python from the environment name
 # and override any basepython configured in this file
 ignore_basepython_conflict = true