Updating platform_offset for BQ printers

Fixes the reason why the Cura UI freezes when choosing my printer from
the wizard.

resources/definitions/bq_hephestos_xl.def.json

@@ -10,12 +10,7 @@
         "category": "Other",
         "file_formats": "text/x-code",
         "platform": "bq_hephestos_platform.stl",
-        "platform_offset": {
-            "value": [
-                0,
-                -82,
-                0
-            ]
+        "platform_offset": [ 0, -82, 0]
         }
     },