Use a machine with less RAM

[valyala]

JSONBench is recommended to run on m6i.8xlarge machine with 128GB of RAM. These amounts of RAM is enough to cache the whole dataset stored on disk in the OS page cache. For example, ClickHouse compresses the dataset to ~100GiB. This doesn't reflect the typical use case for large-scale JSON databases, where they store much more data than the available RAM. There are two options to make the benchmark closer to this use case: either increase the dataset size or decrease the amounts of RAM available to the tested database. The first approach may be too slow, so let's reduce the available RAM to 32GiB or to 16GiB.