Remove reno job and cap tox to version lower than 4

It does not make sense to run it on bugfix branches.
Tox is capped in all stable branches, let's cap it here as well.

Change-Id: If8012b54f666e65e563848fbdb1d4a4e6ec33d1c

tox.ini

@@ -1,8 +1,9 @@
 [tox]
 minversion = 3.18.0
-skipsdist = True
 envlist = py3,pep8,functional-py38
 ignore_basepython_conflict=true
+requires =
+  tox<4
 
 [testenv]
 basepython = python3

zuul.d/project.yaml

@@ -5,7 +5,6 @@
       - openstack-lower-constraints-master-branch-jobs
       - openstack-python3-yoga-jobs-ironic-bugfix19
       - publish-openstack-docs-pti
-      - release-notes-jobs-python3
     check:
       jobs:
         - ironic-inspector-grenade