Always prefer 0.4mm nozzles at initial loading

Otherwise we might end up with 0.8mm AA cores, and those don't have a normal quality profile so that gives all sorts of trouble.

resources/definitions/ultimaker3.def.json

@@ -17,7 +17,7 @@
         "has_machine_materials": true,
         "has_variant_materials": true,
         "has_variants": true,
-        "preferred_variant": "*aa*",
+        "preferred_variant": "*aa04*",
         "preferred_quality": "*Normal*",
         "variants_name": "Print core",
         "machine_extruder_trains":

resources/definitions/ultimaker3_extended.def.json

@@ -18,7 +18,7 @@
         "has_variant_materials": true,
         "has_materials": true,
         "has_variants": true,
-        "preferred_variant": "*aa*",
+        "preferred_variant": "*aa04*",
         "variants_name": "Print core",
         "machine_extruder_trains":
         {