fix: ray module not found handling (meta-pytorch#1049)

Differential Revision: D73751531

Pull Request resolved: meta-pytorch#1055

Author: andywag

docs/source/schedulers/ray.rst

@@ -13,7 +13,6 @@ Ray
       :show-inheritance:
 
    .. autofunction:: create_scheduler
-   .. autofunction:: has_ray
    .. autofunction:: serialize
 
    .. autoclass:: RayJob