Ignore actual processor speed when comparing machine_info

[jontwo]

I've just added pytest-benchmark to our CI, following the GDAL approach where we install an old version, run benchmarks, then install latest version, run benchmarks again and compare. I'm getting the following warning because the hz_actual is slightly different between the two runs: "PytestBenchmarkWarning: Benchmark machine_info is different".

I'm running the two tests on exactly the same machine, one after the other, so I would not expect a warning that the machines are different! Is it possible to ignore the hz_actual and hz_actual_friendly fields when comparing cpu_info?