[SPARK-3677] [BUILD] [YARN] pom.xml and SparkBuild.scala are wrong : Scalastyle is never applied to the sources under yarn/common

When we run "sbt -Pyarn scalastyle" or "mvn package", scalastyle is not applied to the sources under yarn/common.
Now I have checked whether I can build successfully without settings 'YARNStable' and 'YARNAlpha' and I confirmed I can build successfully though I couldn't build.
So, I'll remove the settings.