How do I hide the software update notification in system preference?

I recently downloaded Catalina to my iMac and it screwed everything up, so I had to revert back to Mojave. Ever since I went back, I keep getting that software update notification that pops up in system preferences. I used to the command to hide the Catalina update from the software section so I wouldn't accidentally download it again. The Catalina update is missing, but I am still getting that notification that's in my system preferences that an update is still available. Does anyone know how to get rid of that?