SI-5293 delete flaky collection performance tests

timing-based tests like these are way too sensitive to how many tests
are running in parallel, random disturbances in the AWS force (?),
and so forth.

the result being recurring intermittent failures such as
  java.lang.AssertionError: assertion failed: scalaparset: 491535200 vs. javaset: 59864300
from
  https://scala-ci.typesafe.com/job/scala-2.12.x-integrate-windows/361/consoleFull

Rex and Adriaan both suggested simply deleting the tests, rather than
putting them in "pending" purgatory ("benchmarks do not belong in the
partest suite", period)

Author: SethTisue