[4.2] Backup confirm message

[brianteeman]

PR for the last remaining part of #36151

[toivo]

I have tested this item ✅ successfully on e0755e1

Tested successfully in Joomla 4.2.0-beta2-dev of 15 June using PHP 8.0.15.

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[alikon]

I have tested this item ✅ successfully on e0755e1

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[alikon]

RTC

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[richard67]

Thanks all.