Exclude bot users from `User#gitlab_employee?` method

Summary

User#gitlab_employee? is used to display a "GitLab Team Member" badge on the frontend (see #212259 (closed)) but if a bot user has an @gitlab.com email address then it will get the "GitLab Team Member" badge.

These are bots I could find (with an exception of a few actual users): https://gitlab.com/gitlab-org/gitlab/-/project_members?utf8=%E2%9C%93&search=bot

Steps to reproduce

https://staging.gitlab.com/gitlab-org/gitlab/-/issues/3682

What is the current bug behavior?

User#gitlab_employee? returns true for a bot that has a @gitlab.com email

What is the expected correct behavior?

User#gitlab_employee? should return false for a bot that has a @gitlab.com email

Possible fixes

Possibly add a regex check to exclude users that have a username that starts with gitlab and ends with bot.