The notification will remain on under device settings.
However, please kindly disable the "Auto Update overnight" feature so that the device won't get upgraded to the new version automatically.
Setting method:
realme UI 3.0 & above versions: Settings > About phone, click realme UI/Up to date at the top > click 
in the upper right corner > Auto update > Auto-update overnight
realme UI 1.0 & 2.0: Settings > Software update > Click the Settings in the upper right corner> Auto-update overnight.
realme UI T & U Edition: Settings > System > Software update > Click the Settings button in the upper right corner > Auto-update overnight.
realme UI R & Go & S Edition: not support. You can manually update system. Settings > System update
