Resolve "QA: Deploy key cloning test sometimes can't find the QA element"

What does this MR do?

This improves a previous fix that was not working correctly. Instead of trying to find the element we only check if the CSS is present yet.

Are there points in the code the reviewer needs to double check?

I don't think so.

Why was this MR needed?

Because using Capybara's find, we get an Capybara::ElementNotFound error, but here that's not what we want since we are in a wait loop, we actually want to perform a non-raising-exception check.

Does this MR meet the acceptance criteria?

• [-] Changelog entry added, if necessary => No need for a changelog for QA change
• Conform by the code review guidelines
  • Has been reviewed by a Backend maintainer
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #48243 (closed)