Check Revert button is enabled in MR revert test

What does this MR do and why?

There is a transient E2E test failure in #366352 (closed). Very, occasionally the revert button click does not occur and the revert modal is not displayed. This MR ensures that the revert button is present and enabled before attempting to click revert.

Screenshots or screen recordings

Re-tested against local GDK and staging

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.