Change icon on clear connections

We're updating the icon for the “Clear Connections” action in the multi-step toolbar.

Currently, it uses a trash icon, which can be misleading—users may assume it will delete steps. We're replacing it with a blank link icon to more accurately represent its true function: removing the connection lines between steps while keeping the steps intact.

This change will make the interface more intuitive, helping users confidently manage workflows without the fear of deleting content.