Docs: Use "sphinx_rtd_theme" instead of "classic"

Author: mgeier

doc/conf.py

@@ -133,7 +133,7 @@
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme = 'classic'
+html_theme = 'sphinx_rtd_theme'
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the