Fix small leak in explode (#10245)

This fixes #10244 you can look at that for the analysis of the bug.

Authors:
  - Robert (Bobby) Evans (https://github.com/revans2)

Approvers:
  - David Wendt (https://github.com/davidwendt)
  - Ram (Ramakrishna Prabhu) (https://github.com/rgsl888prabhu)

URL: #10245

cpp/src/lists/explode.cu

@@ -65,7 +65,7 @@ std::unique_ptr<table> build_table(
                    stream,
                    mr);
 
-  std::vector<std::unique_ptr<column>> columns = gathered_table.release()->release();
+  std::vector<std::unique_ptr<column>> columns = gathered_table->release();
 
   columns.insert(columns.begin() + explode_column_idx,
                  explode_col_gather_map