message: update_agent: improve linewrapping of logout warning
  Keep all lines to 80 characters.
diff: @@ -506,9 +506,10 @@ fn format_reboot_warning(seconds: u64, release_ver: &str) -> String {
  format!(
  "New update {} is available and has been deployed.\n\
  - If permitted by the update strategy, Zincati will reboot into this update when all\n\
  - interactive users have logged out, or in {}, whichever comes earlier.\n\
  - Please log out of all active sessions in order to let the auto-update process continue.",
  + If permitted by the update strategy, Zincati will reboot into this update when\n\
  + all interactive users have logged out, or in {}, whichever comes\n\
  + earlier. Please log out of all active sessions in order to let the auto-update\n\
  + process continue.",
  release_ver, time_till_reboot
  )
  }
  