documentation: bump sphinx version

doc/conf.py

@@ -66,6 +66,3 @@ html_theme = "sphinx_rtd_theme"
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ["_static"]
-
-# Disable contents.rst for forward compatibility
-master_doc = "index"

requirements.txt

@@ -22,5 +22,5 @@ sentry_sdk
 # mysqlclient
 
 # For documentation
-Sphinx < 2.0 # To ensure compatibility with reathedocs
+Sphinx > 2.0
 sphinx_rtd_theme