Fix: anonymous attribute output requested even though it's not used

The code removed here was intended to be an optimization that
avoids creating an additional node to join multiple attribute sets.
However, that optimization did not work, because it did not take
into account whether the single attribute set is required or not.

source/blender/nodes/intern/geometry_nodes_lazy_function.cc

@@ -2523,9 +2523,6 @@ struct GeometryNodesLazyFunctionGraphBuilder {
     if (attribute_set_sockets.is_empty()) {
       return nullptr;
     }
-    if (attribute_set_sockets.size() == 1) {
-      return attribute_set_sockets[0];
-    }
 
     Vector<lf::OutputSocket *, 16> key;
     key.extend(attribute_set_sockets);