Login to your Gitlab > Admin area > settings > Features > remove the check mark "Signup enabled"
Source page: https://forum.gitlab.com/t/disable-user-creation-on-welcome-page/806
Login to your Gitlab > Admin area > settings > Features > remove the check mark "Signup enabled"
Source page: https://forum.gitlab.com/t/disable-user-creation-on-welcome-page/806