remove cupy backend

Author: statusfailed

open_hypergraphs/array/__init__.py

@@ -1,10 +1,5 @@
 """Array backends for :ref:`open_hypergraphs.finite_function`.
 
-Each sub-module of :ref:`open_hypergraphs.array` is an "array backend".
-Array backends provide a small number of *primitive functions*
-like :func:`open_hypergraphs.array.numpy.zeros` and :func:`open_hypergraphs.array.numpy.arange` .
-See :ref:`open_hypergraphs.array.numpy` (the default backend) for a list.
-
 .. warning::
    This part of the API is likely to change significantly in future releases.
 
@@ -13,5 +8,4 @@
     :recursive:
 
     open_hypergraphs.array.numpy
-    open_hypergraphs.array.cupy
 """