Increase warning value for outer wall wipe distance

For polypropylene a wipe distance of twice the nozzle size is fine. Even required, since the material warps so much that it breaks open automatically if a breach starts to appear at the seam. For other warping materials this could also be a problem, so let's just increase the warning value.

Contributes to issue CURA-3960.

resources/definitions/fdmprinter.def.json

@@ -858,7 +858,7 @@
                     "default_value": 0.2,
                     "value": "machine_nozzle_size / 2",
                     "minimum_value": "0",
-                    "maximum_value_warning": "machine_nozzle_size",
+                    "maximum_value_warning": "machine_nozzle_size * 2",
                     "settable_per_mesh": true
                 },
                 "top_bottom_thickness":