format timestamp as date to make it more easy to read in systemCheckPage #19256

Description:

Make it easier to read and understand when latest archiving was done.

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

If you don't want this PR to be closed automatically in 28 days then you need to assign the label 'Do not close'.

If you don't want this PR to be closed automatically in 28 days then you need to assign the label 'Do not close'.