Use latest GitLab Runner image from registry.gitlab.com in E2E tests

What does this MR do and why?

Revert "Merge branch 'sv-downgrade-runner-qa-tests' into 'master'" - this MR reverts the QA tests to using a fixed version of gitlab-runner back to using the latest version of the runner. See gitlab-com/gl-infra/production#8421 (closed)

Use latest version of gitlab-runner in tests. 15.9.0 was causing issues in the tests, 15.9.1 is now released and is working.

This MR also ensures the GitLab Runner image is being pulled from registry.gitlab.com

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