These Esko-supplied marks are included in the Dynamic Marks plugin bundle and can be removed from there.
On Mac: Open /Applications/Adobe Illustrator CC XXXX/Esko/DynamicMarks.plugin (right-click to open the contextual menu, then Show Package Contents) and browse to Contents/Resources/MarkSets.
On Windows: Browse to C:\Program Files\Adobe\Adobe Illustrator CC XXXX\Esko\DynamicMarks.plugin\MarkSets.
They will be copied again to that location on the next update or re-installation of Dynamic Marks.