fix dependencies.

requirements_rtd.txt

@@ -13,6 +13,6 @@ rdflib==4.2.2
 requests-toolbelt>=0.8.0
 requests>=2.18.4
 sphinx-rtd-theme>=0.2.4
-sphinxcontrib-yaml>=1.0.0
+sphinxcontrib-autoyaml
 stomp.py>=4.1.20
 wheel>=0.30.0a0