[chiselsim] Remove defeault value in Settings

Remove a default value in Settings.  This should not have been set as this
class has a default factory.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>

Author: seldridge

src/main/scala/chisel3/simulator/Settings.scala

@@ -88,7 +88,7 @@ final class Settings[A <: RawModule] private[simulator] (
   val printfCond:            Option[MacroText.Type[A]],
   val stopCond:              Option[MacroText.Type[A]],
   val plusArgs:              Seq[svsim.PlusArg],
-  val enableWavesAtTimeZero: Boolean = false
+  val enableWavesAtTimeZero: Boolean,
 ) {
 
   def copy(