docs: Make font link protocol agnostic

docs/_themes/attic/sidebarlogo.html

@@ -1,4 +1,4 @@
-<link href='http://fonts.googleapis.com/css?family=Oswald:700|Inconsolata:400,700'
+<link href='//fonts.googleapis.com/css?family=Oswald:700|Inconsolata:400,700'
           rel='stylesheet' type='text/css'>
 <div class="sidebarlogo">
   <a href="{{ pathto('index') }}">