[C++] Remove redundant code from the benchmark

[pandalee99]

Feature Request

cpp/fory/benchmark/benchmark_string_util.cc

In the fory-cpp module, in the benchmark file, simdutf is used for performance comparison. However, in reality, we do not use this library function. We are considering further removing it.

Is your feature request related to a problem? Please describe

We can run a benchmark once before removing the simdutf dependency as a performance report.

Describe the solution you'd like

No response

Describe alternatives you've considered

No response

Additional context

If we think this is necessary, perhaps we can set it as good first issue. cc @chaokunyang

[chaokunyang]

I don' think it's a task that new contributor would be interested, we can just remove it directly