Get rid of collective.portlet.relateditems

[sauzher]

Product abandoned: https://github.com/collective/collective.portlet.relateditems

I found only one assigment of collective.portlet.relateditems portlet here in staging

/isaw/skunkworks/portlet-experiments/page-for-related
     manager: plone.leftcolumn
     id: related-items
     uid/ref: <Document at /isaw/skunkworks/portlet-experiments/page-for-related>

I think this product could be removed from the project. It has AT dependency and is abandoned.

[paregorios]

Fine by me to remove this product