minor: small change to ToCupy docstring

Author: mrava87

pylops/basicoperators/tocupy.py

@@ -13,7 +13,7 @@
 class ToCupy(LinearOperator):
     r"""Convert to CuPy.
 
-    Convert an input array to CuPy in forward mode,
+    Convert an input NumPy array to CuPy in forward mode,
     and convert back to NumPy in adjoint mode.
 
     Parameters