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
before the next release removes them. A couple of variables are also
not needed anymore, remove them.

Set openstackdocs_auto_name to use 'project' as name.

Depends-On: https://review.opendev.org/728938
Change-Id: If90af1920749efd1b314884a4b366d6d2c939521

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.
 # These are needed for docs generation
-openstackdocstheme>=1.18.1 # 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

doc/source/conf.py

@@ -27,9 +27,9 @@ extensions = [
 ]
 
 # openstackdocstheme options
-repository_name = 'openstack/oslo.serialization'
-bug_project = 'oslo.serialization'
-bug_tag = ''
+openstackdocs_repo_name = 'openstack/oslo.serialization'
+openstackdocs_bug_project = 'oslo.serialization'
+openstackdocs_bug_tag = ''
 
 # autodoc generation is a bit aggressive and a nuisance when doing heavy
 # text edit cycles.
@@ -64,7 +64,6 @@ pygments_style = 'sphinx'
 # html_static_path = ['static']
 html_theme = 'openstackdocs'
 
-html_last_updated_fmt = '%Y-%m-%d %H:%M'
 
 # Output file base name for HTML help builder.
 htmlhelp_basename = '%sdoc' % project

releasenotes/source/conf.py

@@ -40,9 +40,10 @@ extensions = [
 ]
 
 # openstackdocstheme options
-repository_name = 'openstack/oslo.serialization'
-bug_project = 'oslo.serialization'
-bug_tag = ''
+openstackdocs_repo_name = 'openstack/oslo.serialization'
+openstackdocs_bug_project = 'oslo.serialization'
+openstackdocs_bug_tag = ''
+openstackdocs_auto_name = False
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
@@ -146,10 +147,6 @@ html_static_path = ['_static']
 # directly to the root of the documentation.
 # html_extra_path = []
 
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
-html_last_updated_fmt = '%Y-%m-%d %H:%M'
-
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.
 # html_use_smartypants = True