Add note about casting to ArrayLike for Python 3.10 mypy

Author: matthewfeickert

src/pyhf/tensor/numpy_backend.py

@@ -656,4 +656,5 @@ def transpose(self, tensor_in: Tensor[T]) -> ArrayLike:
 
         .. versionadded:: 0.7.0
         """
+        # TODO: Casting needed for Python 3.10 mypy but not Python 3.13?
         return cast(ArrayLike, tensor_in.transpose())