[Peek] Fix for DateModified tooltip property showing file creation date

[daverayment]

Summary of the Pull Request

The Peek image preview shows an infotip on hover, including a Date Modified field. This was incorrectly set to the file's creation date.

PR Checklist

• [x] Closes: #34494
• [ ] Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• [ ] Tests: Added/updated and all pass
• [ ] Localization: All end user facing strings can be localized
• [ ] Dev docs: Added/updated
• [ ] New binaries: Added on the required places
  • [ ] JSON for signing for new binaries
  • [ ] WXS for installer for new binaries and localization folder
  • [ ] YML for CI pipeline for new test projects
  • [ ] YML for signed pipeline
• [ ] Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

This was a simple change to return GetLastWriteTime for the file.

Validation Steps Performed

Manual validation by using Peek on an image file where the creation datetime was different to the modified date.