test: minimize time for child_process benchmark

test-benchmark-child-process sometimes times out on Windows in CI.
Minimize the number of configurations that run so it will (hopefully)
not time out anymore. Set dur=0.

PR-URL: https://github.com/nodejs/node/pull/12518


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>