Remove unknown sign from the JSON beginnings

Otherways the js JSON parse method returns `SyntaxError: Unexpected token  in JSON at position 0` error.

Common/UnitDefinitions/ThermalConductivity.json

@@ -1,4 +1,4 @@
-{
+{
   "Name": "ThermalConductivity",
   "BaseUnit": "WattPerMeterKelvin",
   "XmlDoc": "Thermal conductivity is the property of a material to conduct heat.",
@@ -35,4 +35,4 @@
       ]
     }
   ]
-}
+}