Sync releasenotes tox env with previous zuul job command

Since the switch [1] we're observing inconsistent builds
in stable branches.

[1]: I98127c5976332770fa6b42513714a05df6587421

Change-Id: I24d1dab10f813f5eaeb511ff13dd75e206ca580c
Co-authored-by: Michal Nasiadka <mnasiadka@gmail.com>
Co-authored-by: Dmitriy Chubinidze <dcu995@gmail.com>
Signed-off-by: Ivan Anfimov <lazekteam@gmail.com>

tox.ini

@@ -5,7 +5,9 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-allowlist_externals = {toxinidir}/tools/tox_install.sh
+allowlist_externals =
+  {toxinidir}/tools/tox_install.sh
+  rm
 install_command = {toxinidir}/tools/tox_install.sh {env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master} {opts} {packages}
 deps =
   -r{toxinidir}/requirements.txt
@@ -38,6 +40,9 @@ builtins = _
 exclude = .venv,.git,.tmp,.tox,dist,doc,*lib/python*,*egg,tools
 
 [testenv:releasenotes]
-deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
-       -r{toxinidir}/doc/requirements.txt
-commands = sphinx-build -a -E -W -d releasenotes/build/doctrees --keep-going -b html releasenotes/source releasenotes/build/html
+install_command = pip install {opts} {packages}
+deps =
+  -r{toxinidir}/doc/requirements.txt
+commands =
+  rm -rf releasenotes/build
+  sphinx-build -W --keep-going -b html -j auto releasenotes/source releasenotes/build/html