GmailApp.sendEmail prevent confirmation tab from opening

When my script uses GmailApp.sendEmail a new tab opens with a message even though I have commented out the return ContentService.createTextOutput ("Auto Reply Send Successfully!"); line

How do I make this not happen ?

  var recipientEmail = e.parameter.email;
  var subject = "Red Tool Response OK";
  var body = "I'm not 100%, but I think I can manage.";
  
  // Send an auto-reply to the sender (yourself)
  GmailApp.sendEmail(recipientEmail, subject, body);
  
  // Confirmation message shown after button click
  //return ContentService.createTextOutput("Auto Reply Sent Successfully!");
}```