Switch to newer openstackdocstheme and reno versions

Switch to openstackdocstheme 2.2.1 and reno 3.1.0 versions. Using
these versions 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: I8a1ab16a84cdbbaf7b22b5dc58aab54980866415

doc/requirements.txt

@@ -3,5 +3,5 @@
 # process, which may cause wedges in the gate later.
 
 sphinx>=2.0.0,!=2.1.0 # BSD
-openstackdocstheme>=2.0.0 # Apache-2.0
-reno>=2.5.0 # Apache-2.0
+openstackdocstheme>=2.2.1 # Apache-2.0
+reno>=3.1.0 # Apache-2.0

releasenotes/source/conf.py

@@ -41,9 +41,8 @@ master_doc = 'index'
 copyright = u'2013, Sahara Developers'
 
 # openstackdocstheme options
-repository_name = 'openstack/sahara-dashboard'
-bug_project = '936'
-bug_tag = ''
+openstackdocs_repo_name = 'openstack/sahara-dashboard'
+openstackdocs_use_storyboard = True
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -75,7 +74,7 @@ exclude_patterns = []
 # 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 = []