Update redis-rack to 2.0.4

What does this MR do?

This updates redis-rack to 2.0.4

Why was this MR needed?

Versions prior to 2.0.3 mess up the rake command outside of GitLab.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together