SPARK-3404 [BUILD] SparkSubmitSuite fails with "spark-submit exits with code 1"

This fixes the `SparkSubmitSuite` failure by setting `<spark.ui.port>0</spark.ui.port>` in the Maven build, to match the SBT build. This avoids a port conflict which causes failures.

(This also updates the `scalatest` plugin off of a release candidate, to the identical final release.)
Nah, this is not necessary to back-port.