MINOR: Remove unused `scalatest` definition from `dependencies.gradle` (#10655)
MINOR: Remove unused `scalatest` definition from `dependencies.gradle` (#10655)

Related PR where the `scalatest` usage was removed: #9858

Reviewers: Ismael Juma <0794a5c7e497910d682bf2c54c66cc30760c0221@juma.me.uk>
apache/kafka,TiVo/kafka,guozhangwang/kafka,apache/kafka,lindong28/kafka,TiVo/kafka,lindong28/kafka,guozhangwang/kafka,guozhangwang/kafka,apache/kafka,guozhangwang/kafka,lindong28/kafka,lindong28/kafka,apache/kafka,TiVo/kafka,TiVo/kafka