modify .readthedocs.yaml to include requirements

.readthedocs.yaml

@@ -31,6 +31,6 @@ sphinx:
 # Optional but recommended, declare the Python requirements required
 # to build your documentation
 # See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
-# python:
+python:
    install:
    - requirements: docs/requirements.txt