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/ElectricPotentialDc.json

@@ -1,4 +1,4 @@
-{
+{
   "Name": "ElectricPotentialDc",
   "BaseUnit": "VoltDc",
   "XmlDoc": "The Electric Potential of a system known to use Direct Current.",
@@ -17,4 +17,4 @@
       ]
     }
   ]
-}
+}