Make Imre Farkas a backend maintainer

• I have been a GitLab team member for almost 1.5 year, most of it in the devopsmanage team
• During this period, I authored at least 97 merge requests
• Opened my trainee maintainer issue 6 months ago, and reviewed at least 88 merge requests

My review skills have improved significantly, and I learned a lot about our codebase. I sometimes miss a thing or two but most of them are minor and the merge request is already up to our standards.

Trainee issue: #4230 (closed)