Hide gradual infill when cubic subdivision infill pattern is selected

The setting has no effect then, so it doesn't matter what the value is while it's hidden either.

Contributes to issue CURA-2602.

resources/definitions/fdmprinter.def.json

@@ -1132,7 +1132,7 @@
                     "minimum_value": "0",
                     "maximum_value_warning": "4",
                     "maximum_value": "20 - math.log(infill_line_distance) / math.log(2)",
-                    "enabled": "infill_sparse_density > 0",
+                    "enabled": "infill_sparse_density > 0 and infill_pattern != 'cubicsubdiv'",
                     "settable_per_mesh": true
                 },
                 "gradual_infill_step_height":
@@ -1145,7 +1145,7 @@
                     "minimum_value": "0.0001",
                     "minimum_value_warning": "3 * resolveOrValue('layer_height')",
                     "maximum_value_warning": "100",
-                    "enabled": "infill_sparse_density > 0 and gradual_infill_steps > 0",
+                    "enabled": "infill_sparse_density > 0 and gradual_infill_steps > 0 and infill_pattern != 'cubicsubdiv'",
                     "settable_per_mesh": true
                 },
                 "infill_before_walls":