:warning: Add a 'home-made' disclaimer on auto-update

Guides/install-linux.md

@@ -115,3 +115,5 @@ Edit the root crontab :
 0 3 * * 4 /home/jovian/Cron/reboot_system > /home/jovian/Cron/logs/reboot_system_log.txt 2> /home/jovian/Cron/logs/reboot_system_error.txt
 @reboot /home/jovian/Cron/boot_system > /home/jovian/Cron/logs/reboot_system_log.txt 2> /home/jovian/Cron/logs/reboot_system_error.txt
 ```
+
+Note : it's a home-made solution. Prefer `unattended-upgrades` for real use cases.