default passwordless wallet for utl_http in Oracle

Question

I have Oracle 18c and by default the following fails with ORA-29024: Certificate validation failure:

DECLARE
  req utl_http.req;
  res utl_http.resp;
BEGIN
  req := utl_http.begin_request('https://linux.die.net/', 'GET',' HTTP/1.1');
  res := utl_http.get_response(req);
  DBMS_OUTPUT.put_line(res.status_code);
END;
/

I followed this article and created a wallet with the needed certificate. However, I don't want to call UTL_HTTP.set_wallet() every time, I want it to be there by default. There was already an empty directory ${ORACLE_HOME}/data/wallet. Is it the default location? Then how to create a passwordless wallet there?