code: public TableDescription deleteGSI() {
          return table.updateTable(new UpdateTableSpec()
              .withGlobalSecondaryIndexUpdates(
                  new GlobalSecondaryIndexUpdate().withDelete(
                      new DeleteGlobalSecondaryIndexAction()
                      .withIndexName(indexName))));
      }
docs: Deletes this global secondary index (GSI) from the DynamoDB table.
  Involves network calls.
  <p>
  This index must be a global secondary index and in the
  <code>ACTIVE</code> state for this operation to succeed. Deleting a GSI
  is an asynchronous operation; while executing the operation, the index is
  in the <code>DELETING</code> state.
  
  @return the updated table description returned from DynamoDB.