message: Issue Fix Memory Leak
  Close and destroy the appender.
diff: @@ -418,6 +418,12 @@ TEST_CASE("Test append timestamp in C API", "[capi]") {
  status = duckdb_appender_flush(appender);
  REQUIRE(status == DuckDBSuccess);
  + status = duckdb_appender_close(appender);
  + REQUIRE(status == DuckDBSuccess);
  +
  + status = duckdb_appender_destroy(&appender);
  + REQUIRE(status == DuckDBSuccess);
  +
  result = tester.Query("SELECT * FROM test");
  REQUIRE_NO_FAIL(*result);
  REQUIRE(result->Fetch<string>(0, 0) == "2022-04-09 15:56:37.544");
  