Fix setup_postgresql.rake missing require

What does this MR do?

Adds a missing require line to setup_postgresql.rake.

Why was this MR needed?

This bug was caught in CE but I must have dropped the ball in ensuring it was fixed for EE as well.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Fixes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/233