BUG: Subject hierarchy does not try to remove non-SH hierarchy nodes when data node is deleted

When a (non-SH) node is removed, the related subject hierarchy node is removed with it, so that it's not left dangling and become invalid. Previously the occasional other type hierarchy nodes were removed as well. This has caused problems when deleting the nodes in other modules handling hierarchies due to different handling of node deletion, so this feature has been removed.

Fixes #3918

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23829 3bd1e089-480b-0410-8dfb-8563597acbee