reduce minimum support xy distance

Setting this value smaller could cause scarring when the nozzle offset calibration is not performed. A higher value causes a too big gap between the model and support, resulting in support not being attached to the model on sloped surfaces. PP-185

resources/definitions/ultimaker.def.json

@@ -239,7 +239,7 @@
             "value": "1"
         },
         "support_xy_distance_overhang": {
-            "value": "wall_line_width_0"
+            "value": "0.2"
         },
         "minimum_support_area": {
             "value": "(2 + support_offset)**2"