Remove deprecated code_typet constructor

It has been deprecated for 9 months.

Author: tautschnig

src/util/std_types.h

@@ -737,16 +737,6 @@ class code_typet:public typet
     return_type().swap(_return_type);
   }
 
-  /// \deprecated
-  DEPRECATED(SINCE(2018, 6, 4, "Use the two argument constructor instead"))
-  code_typet():typet(ID_code)
-  {
-    // make sure these properties are always there to avoid problems
-    // with irept comparisons
-    add(ID_parameters);
-    add_type(ID_return_type);
-  }
-
   // used to be argumentt -- now uses standard terminology
 
   class parametert:public exprt