Switch to newer openstackdocstheme and reno versions

Switch to openstackdocstheme 2.2.0 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.

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

Depends-On: https://review.opendev.org/728938
Change-Id: If23ebf2dcf6304d5ea50c5e427bfad217ce0d235

doc/requirements.txt

@@ -2,7 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 # These are needed for docs generation
-openstackdocstheme>=1.20.0 # Apache-2.0
-sphinx>=1.8.0,!=2.1.0 # BSD
-reno>=2.5.0 # Apache-2.0
+openstackdocstheme>=2.2.0 # Apache-2.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+reno>=3.1.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD

doc/source/conf.py

@@ -72,9 +72,9 @@ latex_documents = [
 ]
 
 # openstackdocstheme options
-repository_name = 'openstack/oslo.context'
-bug_project = 'oslo.context'
-bug_tag = ''
+openstackdocs_repo_name = 'openstack/oslo.context'
+openstackdocs_bug_project = 'oslo.context'
+openstackdocs_bug_tag = ''
 
 # Example configuration for intersphinx: refer to the Python standard library.
 #intersphinx_mapping = {'http://docs.python.org/': None}

releasenotes/source/conf.py

@@ -256,6 +256,6 @@ texinfo_documents = [
 locale_dirs = ['locale/']
 
 # openstackdocstheme options
-repository_name = 'openstack/oslo.context'
-bug_project = 'oslo.context'
-bug_tag = ''
+openstackdocs_repo_name = 'openstack/oslo.context'
+openstackdocs_bug_project = 'oslo.context'
+openstackdocs_bug_tag = ''