remove sphinx deprecation

docs/source/conf.py

@@ -168,7 +168,7 @@
 # Add any paths that contain custom themes here, relative to this directory.
 # html_theme_path = []
 # html_theme_path = ['_themes', ]
-html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
+# html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
 
 # The name for this set of Sphinx documents.
 # "<project> v<release> documentation" by default.