Don't have generic type variables as a comment

The symex_target_equation will merge two types who differ only in
generic specialisation losing the specialisation information. This
ensures that information is kept.

Author: thk123

src/util/irep_ids.def

@@ -655,7 +655,7 @@ IREP_ID_TWO(C_java_implicitly_generic_class_type, #java_implicitly_generic_class
 IREP_ID_TWO(C_java_generic_symbol, #java_generic_symbol)
 IREP_ID_TWO(generic_types, #generic_types)
 IREP_ID_TWO(implicit_generic_types, #implicit_generic_types)
-IREP_ID_TWO(type_variables, #type_variables)
+IREP_ID_ONE(type_variables)
 IREP_ID_TWO(java_lambda_method_handle_index, lambda_method_handle_index)
 IREP_ID_TWO(java_lambda_method_handles, lambda_method_handles)
 IREP_ID_ONE(havoc_object)