I run this sampling 10^6 times. Max repeats was 23.
The code I used:
    (1 to 1000000).map(_ => 1.to(100).flatMap(_ => Sampling.randomSubset(5, (1 to 100).toArray, rng)).groupBy(identity).map{ case (k, v) => v.length}.max).max
I know, I'm actually adjusting test to the results, but number seems reasonable for me and with very high prob the test won't fail. What do you think?