Switch to newer openstackdocstheme version

Switch to openstackdocstheme 2.2.1 version. Using
this version will allow especially:
* Linking from HTML to PDF document
* Allow parallel building of documents
* Fix some rendering problems

Update Sphinx version as well.

Disable openstackdocs_auto_version to not auto-version the documents.

Disable openstackdocs_auto_name to use 'project' variable as name.

Change pygments_style to 'native' since old theme version always used
'native' and the theme now respects the setting and using 'sphinx' can
lead to some strange rendering.

Remove docs requirements from lower-constraints, they are not needed
during install or test but only for docs building.

openstackdocstheme renames some variables, so follow the renames
before the next release removes them. A couple of variables are also
not needed anymore, remove them.

See also
http://lists.openstack.org/pipermail/openstack-discuss/2020-May/014971.html

Change-Id: I08e76c4c62a53587baa5772675bb9afd37689a80

doc/requirements.txt

@@ -1,3 +1,3 @@
-sphinx!=1.6.6,!=1.6.7,!=2.1.0,>=1.6.2 # BSD
-openstackdocstheme>=1.30.0 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+openstackdocstheme>=2.2.1 # Apache-2.0
 pbr>=1.6 # Apache-2.0

doc/source/conf.py

@@ -80,7 +80,7 @@ add_module_names = False
 show_authors = False
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
+pygments_style = 'native'
 
 # A list of ignored prefixes for module index sorting.
 modindex_common_prefix = ['puppet-openstack-guide.']
@@ -254,3 +254,7 @@ epub_copyright = u'%s, OpenStack Contributors' % datetime.date.today().year
 
 # Allow duplicate toc entries.
 #epub_tocdup = True
+
+
+# openstackdocstheme options
+openstackdocs_repo_name = 'openstack/puppet-openstack-guide'