chore: add wait for flaky relationship management test

[paula-stacho]

Description

The relationship management tests seems to be flaky in CI. I can't reproduce it locally, and I don't see anything wrong in the screenshot so I'm just adding a couple of waits around where it gets stuck. If nothing else, it might help us locate the problem.

Checklist

• New tests and/or benchmarks are included
• Documentation is changed or added
• If this change updates the UI, screenshots/videos are added and a design review is requested
• I have signed the MongoDB Contributor License Agreement (https://www.mongodb.com/legal/contributor-agreement)

Motivation and Context

• Bugfix
• New feature
• Dependency update
• Misc

Open Questions

Dependents

Types of changes

• Backport Needed
• Patch (non-breaking change which fixes an issue)
• Minor (non-breaking change which adds functionality)
• Major (fix or feature that would cause existing functionality to change)

[Copilot]

Pull Request Overview

This PR addresses flaky test behavior in the relationship management tests by adding wait conditions to ensure UI elements are properly loaded before interaction. The changes focus on making the test more robust in CI environments where timing issues may occur.

• Adds waitForClickable() to ensure the edit button is interactive before clicking
• Extracts the foreign cardinality select element to a variable and adds waitForDisplayed() before using it

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}