Remove unused ID_string_not_contains_constraint

Author: romainbrenguier

src/util/irep_ids.def

@@ -582,7 +582,6 @@ IREP_ID_ONE(push_catch)
 IREP_ID_ONE(pop_catch)
 IREP_ID_ONE(exception_landingpad)
 IREP_ID_ONE(length_upper_bound)
-IREP_ID_ONE(string_not_contains_constraint)
 IREP_ID_ONE(cprover_associate_array_to_pointer_func)
 IREP_ID_ONE(cprover_associate_length_to_array_func)
 IREP_ID_ONE(cprover_char_literal_func)