"GitLab Alert Bot" should not be displayed in the user list

Summary

GitLab Alert Bot "ghost user" shows up in the list of users causing confusion about the user count.

Original Bug Report

A "GitLab Alert Bot" user was created. I want to get rid of it but it 404s.

I've noticed that the number of users went up by one with registration being disabled. The new user is called "GitLab Alert Bot". I have no idea what it does (what's an alert? I haven't received one and I never enabled anything like this), and trying to edit or delete it results in a 404.

Why do you pollute the user list with BS like this, the fake ghost user, etc.?

What is the current bug behavior?

Alert Bot is created and not able to be deleted.

What is the expected correct behavior?

The Alert bot, and all ghost/bot users should be filtered out of the user list.

Possible fixes

Add filtering to the user list, see #211616 (comment 353656107)