Remove waitForCondition when detecting thread leak

discussion: https://github.com/apache/kafka/pull/16499#discussion_r1679676258

Those tests, which are using ClusterTestExtensions, should make sure the threads created by testing get done indeed.

BTW, we need to ensure removing `waitForCondition` won't bring a bunch of failed tests, and hence please feel free to add sub-task if you notice the thread which can cause failure after removing the `waitForCondition`.

The PR for this ticket will also include KAFKA-17187 and KAFKA-17187, so we can make sure there is no leak thread after applying these fix.