[stable-only] Pin tox <4stable/yoga

We pinned tox<4 for stable branches in common jobs
and in devstack playbook but that was not enough for
python client functional jobs where tox is upgraded to
latest by pip.

- https://lists.openstack.org/pipermail/openstack-discuss/2023-January/031678.html

This commit adds tox<4 pin explicitly in tox.ini

Change-Id: I442568a5f5900e593feb2b5527109e0aa79e5aa7
(cherry picked from commit 7c3f3bc615cb91cd0106f91b0452bf7968ff3598)

1 files changed, 1 insertions, 0 deletions

diff --git a/tox.ini b/tox.ini
index 30cde5d4..ff3d8a9b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,7 @@
 [tox]
 envlist = py3,pep8,docs
 minversion = 3.18.0
+requires = tox<4
 skipsdist = true
 ignore_basepython_conflict = true