update ExectionPlan::children impl for DatasetExec

Ref apache/datafusion#10543

Author: Michael-J-Ward

src/dataset_exec.rs

@@ -164,7 +164,7 @@ impl ExecutionPlan for DatasetExec {
         self.schema.clone()
     }
 
-    fn children(&self) -> Vec<Arc<dyn ExecutionPlan>> {
+    fn children(&self) -> Vec<&Arc<dyn ExecutionPlan>> {
         // this is a leaf node and has no children
         vec![]
     }

src/physical_plan.rs

@@ -40,7 +40,7 @@ impl PyExecutionPlan {
         self.plan
             .children()
             .iter()
-            .map(|p| p.to_owned().into())
+            .map(|p| p.clone().to_owned().into())
             .collect()
     }