Reduce minimum value for flow to 0.0001%

CuraEngine can handle that. It's not going to extrude anything, but neither is 5% really.

Contributes to issue CURA-4506.

resources/definitions/fdmprinter.def.json

@@ -2027,7 +2027,7 @@
                     "default_value": 100,
                     "value": "material_flow",
                     "type": "float",
-                    "minimum_value": "5",
+                    "minimum_value": "0.0001",
                     "minimum_value_warning": "50",
                     "maximum_value_warning": "150",
                     "settable_per_mesh": true