I don’t think Avast recognizes the AOS plugin since it can be downloaded as standalone from the Google Web store. That being said, I’d recommending removing and reinstalling the AOS plugin since as far as I know it shouldn’t pop up with a banner unless it finds an infected website.

https://chrome.google.com/webstore/detail/avast-online-security/gomekmidlodglbbmalcneegieacbdmki?hl=en

The Avast Online Security is optional and can be disabled. All the protection comes from the Web Shield. However, the AOS add on gives website reputations in colors and has Ad tracking/web analytic blocking features. There are alternatives to the add-on such as WOT and Do not track me.