[backport] SI-6412 remove flaky test

(cherry-picking commit a03e7a0)

I have repeatedly seen this fail CI runs, including recently

as the comment in the test itself says: "I'm not sure this is a great
way to test for memory leaks, since we're also testing how good
the JVM's GC is, and this is not easily reproduced between
machines/over time"

Author: SethTisue