Fixed json for grid test

test/Grid/general/code_generation/Simulation_op1.json

@@ -20,7 +20,7 @@
                             "hi":               "tile_ubound"},
             "U":           {"source":           "grid_data",
                             "structure_index":  ["CENTER", 1],
-                            "W":                [1, 2]}
+                            "w":                [1, 2]}
         }
     }
 }