do not use deprecated QVariant::operator<

The operator(s) are deprecated in Qt 5.15:
https://doc.qt.io/qt-5/qvariant-obsolete.html#operator-lt

This is untested and Robert might have a better way to clean this up. :-)

moveit_setup_assistant/src/tools/collision_linear_model.cpp

@@ -273,7 +273,16 @@ bool SortFilterProxyModel::lessThan(const QModelIndex& src_left, const QModelInd
     if (value_left == value_right)
       continue;
 
-    bool smaller = (value_left < value_right);
+    bool smaller{};
+    switch (value_left.type())
+    {
+      case QVariant::Int:
+        smaller = value_left.toInt() < value_right.toInt();
+        break;
+      default:
+        smaller = value_left.toString() < value_right.toString();
+        break;
+    }
     if (sort_orders_[i] == Qt::DescendingOrder)
       smaller = !smaller;
     return smaller;