Fix broken link (#35973)

Apple's URL doesn't work anymore.

website/config/routes.js

@@ -999,7 +999,7 @@ module.exports.routes = {
   'GET /learn-more-about/install-google-play-apps': 'https://github.com/fleetdm/fleet/issues/25595',
   'GET /learn-more-about/arch-linux-rolling-release': 'https://wiki.archlinux.org/title/Arch_Linux',
   'GET /learn-more-about/google-play-store': 'https://play.google.com/store/apps',
-  'GET /learn-more-about/managed-lost-mode': 'https://it-training.apple.com/tutorials/deployment/dm255/',
+  'GET /learn-more-about/managed-lost-mode': 'https://support.apple.com/en-gb/guide/security/secc46f3562c/web',
   'GET /learn-more-about/android-profile-errors': '/guides/custom-os-settings#partial-failure-android-profiles',
   'GET /learn-more-about/how-to-craft-android-profile': '/guides/custom-os-settings#create-configuration-profile',
   'GET /learn-more-about/example-android-profile': 'https://gist.github.com/marko-lisica/45ee31f6850e1f002141c1b5b43ce519',