Revert typo in wave3d_b.py custom topology.

fast/wave3d_b.py

@@ -51,7 +51,7 @@
 if args.xdsl:
     topology = ('*', '*', 1)
 
-grid = Grid(shape=(nx, ny, nz), extent=(2., 2., 2.), topology=topology)
+grid = Grid(shape=shape, extent=(2., 2., 2.), topology=topology)
 
 # With the velocity and model size defined, we can create the seismic model that
 # encapsulates this properties. We also define the size of the absorbing layer as