From the Brushes Preset Preview documentation :

Clean resources in Krita (Edit > Resources > Clean Up removed files)

I don't find it. I guess it's now the "Delete Backup Files" in Settings > Manage Resources but I'm not 100% sure. Also it might be worth updating the wiki in all the pages that refer to this function.

Thanks !

all the default presets are stored here on my windows machine.

C:\Users\spetrovic\Desktop\krita-3.1.2.1-x64\share\krita\paintoppresets

It looks like a krita folder instead of an app folder

Thanks but I didn't ask for a directory. However I updated my first post.