Remove module `aesara.sandbox.neighbour` redirecting to `nnet`

aesara/sandbox/neighbours.py

-"""
-Neighbours was moved into aesara.tensor.nnet.neighbours.
-This file was created for compatibility.
-"""
-
-from aesara.tensor.nnet.neighbours import Images2Neibs, images2neibs, neibs2images
-
-
-__all__ = ["images2neibs", "neibs2images", "Images2Neibs"]