[DNM] Testing docs bump with new Sphinx

Sphinx updates can be scary.  This change leverages a constraints bump to see what breaks.

Depends-On: https://review.opendev.org/c/openstack/requirements/+/916565
Change-Id: I0b00522b7fa52640948aeae1bb05208731b5c6fe

doc/requirements.txt

@@ -4,3 +4,4 @@
 sphinx>=2.0.0,!=2.1.0 # BSD
 openstackdocstheme>=2.2.1 # Apache-2.0
 reno>=3.1.0 # Apache-2.0
+# Force docs rebuild: 

requirements.txt

@@ -27,3 +27,4 @@ pyroute2>=0.5.7;sys_platform!='win32' # Apache-2.0 (+ dual licensed GPL2)
 retrying!=1.3.0,>=1.2.3 # Apache-2.0
 stevedore>=1.20.0 # Apache-2.0
 prometheus_client>=0.6.0 # Apache-2.0
+# Force requirements rebuild: 

setup.py

@@ -18,3 +18,5 @@ import setuptools
 setuptools.setup(
     setup_requires=['pbr>=2.0.0'],
     pbr=True)
+
+# Force unittests: