fix(readthedocs) add a requirement for the python tools needed by shpinx

Signed-off-by: Benoit Mortier <benoit.mortier@fusiondirectory.org>

.readthedocs.yaml

@@ -30,6 +30,6 @@ 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: source/requirements.txt