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: I0b21a468b8952c6189764b8f17bb2ffc057aefec

doc/source/conf.py

@@ -35,12 +35,13 @@ extensions = ['redirect',
              ]
 
 # Settings for openstackdocstheme
-repository_name = 'openstack/charm-specs'
-bug_project = 'charm-specs'
-bug_tag = u''
+openstackdocs_repo_name = 'openstack/charm-specs'
+openstackdocs_auto_name = False
+openstackdocs_bug_project = 'charm-specs'
+openstackdocs_bug_tag = u''
 
 # Feed configuration for yasfb
-feed_base_url = 'http://specs.openstack.org/openstack/charm-specs'
+feed_base_url = 'https://specs.openstack.org/openstack/charm-specs'
 feed_author = 'OpenStack Charm Team'
 
 todo_include_todos = True
@@ -92,7 +93,7 @@ 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 = ['charm-specs.']

requirements.txt

@@ -1,7 +1,7 @@
 pbr>=2.0.0,!=2.1.0  # Apache-2.0
 docutils!=0.13.1,>=0.11 # OSI-Approved Open Source, Public Domain
-openstackdocstheme>=1.31.2  # Apache-2.0
-sphinx>=1.6.2
+openstackdocstheme>=2.2.1 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
 stestr>=2.0.0 # Apache-2.0
 testtools>=1.4.0  # MIT
 yasfb>=0.5.1