Prevent fade out transition on loading-button

What does this MR do?

Disable leave transition in the loading_button component**. The loading icon and button label appear with a fade transition but it disappears with no transition at all. This makes sense since the loading icon appears with a delay because of the asynchronous process that the loading_button triggers may finish immediately. In the other hand, after a response from the asynchronous process is received, the button should transition to its original state immediately.

What are the relevant issue numbers?

Closes #57409 (closed)

To simulate an "Upgrade failure" state, the following commands can be executed:

Open rails console: bundle exec rails console

In rails console execute the following:

1. cluster = Clusters::Cluster.find <id> Note: <id> can be found in the browser url when navigating to the cluster
2. runner = cluster.application_runner
3. runner.update!(status: 6)

The runner on the specified cluster should now be in the update_errored state, and should display the Retry upgrade button

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer