Fix definition of GetVariableResultType.variable (mobilityhouse#316)

Author: HugoJP1

ocpp/v201/datatypes.py

@@ -436,7 +436,7 @@ class GetVariableResultType:
 
     attribute_status: enums.GetVariableStatusType
     component: ComponentType
-    variable = VariableType
+    variable: VariableType
     attribute_type: Optional[enums.AttributeType] = None
     attribute_value: Optional[str] = None
     attribute_status_info: Optional[StatusInfoType] = None