Make it explicit in the logging UI that change in logging levels are not persisted

I have submitted a Pull Request to address this issue: https://github.com/xwiki/xwiki-platform/pull/5190 Changes: - Added an info box in the LoggingAdmin page - Created translation key for the warning message - Warning informs users that logging level changes are temporary The PR is now awaiting review. This work was completed as part of my SOEN 6431 Case Study assignment.