clean up build (use standard source directory names)

recent sbt versions support this directly

Author: SethTisue

build.sbt

@@ -16,16 +16,6 @@ libraryDependencies ++= Dependencies.scalaLogging(scalaVersion.value, isScala3.v
 initialCommands := """|import com.typesafe.scalalogging._
                       |import org.slf4j.{ Logger => Underlying, _ }""".stripMargin
 
-Compile / unmanagedSourceDirectories ++= {
-  val sourceDir = (Compile / sourceDirectory).value
-  val extraFilesOpt = CrossVersion.partialVersion(scalaVersion.value) match {
-    case Some((2, _)) => Some(sourceDir / "scala-2.x")
-    case Some((3, _)) => Some(sourceDir / "scala-3.x")
-    case _ => None
-  }
-  extraFilesOpt.toSeq
-}
-
 // OSGi
 
 import com.typesafe.sbt.osgi.SbtOsgi