To disable notifications run:
$ gsettings set org.gnome.desktop.notifications show-banners false
To enable notification run:
$ gsettings set org.gnome.desktop.notifications show-banners true
To disable notifications run:
$ gsettings set org.gnome.desktop.notifications show-banners false
To enable notification run:
$ gsettings set org.gnome.desktop.notifications show-banners true