Update doc theme settings to match Zuul

This makes the sidebar match the rest of Zuul.

Change-Id: I1ed6f71918d9a4d531ab953ba95e0232d3397e8a

doc/source/conf.py

@@ -77,7 +77,11 @@ latex_documents = [
 
 # The name of an image file (relative to this directory) to place at the top
 # of the sidebar.
-html_logo = '_static/logo.svg'
+#html_logo = '_static/logo.svg'
+html_theme_options = {
+    'show_related': True,
+    'logo': 'logo.svg',
+}
 
 # The name of an image file (within the static path) to use as favicon of the
 # docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32