Big Sur update reminder - How to turn it off?

I've got an early 2015 MacBook Air 4gb with 128 ssd drive. I've always updated the OS when new versions have been released. I'm currently on Catalina and whilst Big Sur appeals, I recognise my Air is getting a bit long in the tooth and may struggle with Big Sur. For that reason, I'm going to pass on the upgrade. My question is though, how do I stop System Preferences reminding me to upgrade? The red dot on the System Preferences icon in the dock is doing my OCD no favours. I obviously want to keep all updates Catalina and other apps, but is there a way to just block the Big Sur reminders? Many thanks.