benchmark: update iteration and size in benchmark/crypto/randomBytes.js
Increase iteration value from 1000 to 10000 to reflect real performance of randomBytes generation. The randomInt has no need to apply this.
Fixes: https://github.com/nodejs/node/issues/50571
Below is the score improvment measured on cascadelake server:
crypto/randomBytes.js size=64: n=10000 percent=137.85%
crypto/randomBytes.js size=1024: n=10000 percent=130.66%
crypto/randomBytes.js size=8192: n=10000 percent=136.31%
crypto/randomBytes.js size=524288: n=10000 percent=166.50%