Success Message is not displayed after countdown when RUCSS is enabled until refresh

[jeawhanlee]

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• Made sure you’re on the latest version - 3.16
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Describe the bug
When RUCSS is enabled and notice with the countdown is displayed, the Success notice will not be displayed after the countdown until the page is refreshed.

To Reproduce
Steps to reproduce the behavior:

1. Enable RUCSS and see the countdown starts.
2. Wait for the countdown
3. See that it stops at 1 and does not display the success notice.
4. Refresh the page and the success notice is displayed.

Expected behavior
The countdown notice should immediately be hidden once the countdown elapsed and the success notice should be displayed.

Screenshots
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Additional context
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Acceptance Criteria (for WP Media team use only)
Clear instructions for developers, to be added before the grooming

[piotrbak]

Duplicate of:
#6633