fix typo in cfg/zstd tester tool

    auto compressed_file = "dump_cfg_zstd_compressed_run0.melt.cfg.zst";

    auto fields = "mass type xs ys zs id proc procp1 x y z ix iy iz vx vy vz fx fy fz";

    generate_text_and_compressed_dump(text_files, compressed_files, "cfg/gz", fields, "", 0);

    generate_text_and_compressed_dump(text_files, compressed_files, "cfg/zstd", fields, "", 0);

    TearDown();