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_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.

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: I46021aa93e28242d0f7dc9d80f598538247a6df5

doc/requirements.txt

@@ -2,6 +2,6 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-sphinx!=1.6.6,!=1.6.7,>=1.6.2  # BSD
+sphinx>=2.0.0,!=2.1.0 # BSD
 sphinxcontrib-blockdiag>=1.1.0
-openstackdocstheme>=1.31.2 # Apache-2.0
+openstackdocstheme>=2.2.1 # Apache-2.0

doc/source/conf.py

@@ -25,8 +25,9 @@ extensions = [
 ]
 
 # openstackdocstheme options
-repository_name = 'openstack/openstack-helm'
-use_storyboard = True
+openstackdocs_repo_name = 'openstack/openstack-helm'
+openstackdocs_auto_name = False
+openstackdocs_use_storyboard = True
 
 # autodoc generation is a bit aggressive and a nuisance when doing heavy
 # text edit cycles.
@@ -54,7 +55,7 @@ add_module_names = True
 show_authors = True
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
+pygments_style = 'native'
 
 # -- Options for HTML output --------------------------------------------------
 # The theme to use for HTML and HTML Help pages.  See the documentation for