change isDeleting to isUnsetting

- DocumentObject::isDeleting was changed to isRemoving.
  This commit just prevents future confusion.

src/Mod/TechDraw/App/DrawProjGroupItem.cpp

@@ -175,7 +175,7 @@ void DrawProjGroupItem::unsetupObject()
     if (getPGroup() != nullptr) {
         if (getPGroup()->hasProjection(Type.getValueAsString()) ) {
             if ((getPGroup()->getAnchor() == this) &&
-                 !getPGroup()->isDeleting() )         {
+                 !getPGroup()->isUnsetting() )         {
                    Base::Console().Warning("Warning - DPG (%s/%s) may be corrupt - Anchor deleted\n",
                                            getPGroup()->getNameInDocument(),getPGroup()->Label.getValue());
                    getPGroup()->Anchor.setValue(nullptr);    //this catches situation where DPGI is deleted w/o DPG::removeProjection