Bump the openstackdocstheme extension to 1.20

Some options are now automatically configured by the version 1.20:
- project
- html_last_updated_fmt
- latex_engine
- latex_elements
- version
- release.

Change-Id: I2e12b3da4686bf9f18d55fbb629d8a4525f3bc8d
diff --git a/doc/source/conf.py b/doc/source/conf.py
index c3cdb16..3a4cff9 100755
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -23,7 +23,6 @@
 extensions = [
     'sphinx.ext.autodoc',
     'openstackdocstheme',
-    #'sphinx.ext.intersphinx',
 ]
 
 # autodoc generation is a bit aggressive and a nuisance when doing heavy
@@ -37,7 +36,6 @@
 master_doc = 'index'
 
 # General information about the project.
-project = u'openstack'
 copyright = u'2017, OpenStack Developers'
 
 # openstackdocstheme options
@@ -65,15 +63,15 @@
 html_theme = 'openstackdocs'
 
 # Output file base name for HTML help builder.
-htmlhelp_basename = '%sdoc' % project
+htmlhelp_basename = 'openstackdoc'
 
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass
 # [howto/manual]).
 latex_documents = [
     ('index',
-     '%s.tex' % project,
-     u'%s Documentation' % project,
+     'openstack.tex',
+     u'openstack Documentation',
      u'OpenStack Developers', 'manual'),
 ]