There seems to be a new dconf setting for the dock in org/gnome.shell.extensions.dash-to-dock
that allows mounts to show.
It's viewable and changeable with
Code:
gsettings get org.gnome.shell.extensions.dash-to-dock show-mounts
to see current value
Default value looks to be true.
Simply set it to false.
Code:
gsettings set org.gnome.shell.extensions.dash-to-dock show-mounts false