Remove unnecessary sleep

I'm not sure what the previous purpose of this was, but syncTo is
blocking so this just seems to add 100ms to the run task startup time.

main/src/main/scala/sbt/internal/DefaultBackgroundJobService.scala

@@ -209,7 +209,6 @@ private[sbt] abstract class AbstractBackgroundJobService extends BackgroundJobSe
     }
     val xs = (products.toVector map { syncTo(workingDirectory / "target") }) ++
       ((full diff products) map { syncTo(serviceTempDir / "target") })
-    Thread.sleep(100)
     xs
   }