Set the default build plate temperature to 0

All third-party materials that didn't fill in a value for this build volume temperature will then default to 0 which causes the printer to go into a safe mode that doesn't melt the plastic or anything.

Contributes to issue CURA-6652.

resources/definitions/fdmprinter.def.json

@@ -2063,7 +2063,7 @@
                     "description": "The temperature of the environment to print in. If this is 0, the build volume temperature will not be adjusted.",
                     "unit": "°C",
                     "type": "float",
-                    "default_value": 35,
+                    "default_value": 0,
                     "resolve": "min(extruderValues('build_volume_temperature'))",
                     "minimum_value": "-273.15",
                     "minimum_value_warning": "0",