chore: drop the -Ycompile-scala2-library flag

Author: hamzaremmal

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -434,7 +434,6 @@ private sealed trait YSettings:
   val YshowTreeIds: Setting[Boolean] = BooleanSetting(ForkSetting, "Yshow-tree-ids", "Uniquely tag all tree nodes in debugging output.")
   val YfromTastyIgnoreList: Setting[List[String]] = MultiStringSetting(ForkSetting, "Yfrom-tasty-ignore-list", "file", "List of `tasty` files in jar files that will not be loaded when using -from-tasty.")
   val YlegacyLazyVals: Setting[Boolean] = BooleanSetting(ForkSetting, "Ylegacy-lazy-vals", "Use legacy (pre 3.3.0) implementation of lazy vals.")
-  val YcompileScala2Library: Setting[Boolean] = BooleanSetting(ForkSetting, "Ycompile-scala2-library", "Used when compiling the Scala 2 standard library.")
   val YprofileEnabled: Setting[Boolean] = BooleanSetting(ForkSetting, "Yprofile-enabled", "Enable profiling.")
   val YprofileDestination: Setting[String] = StringSetting(ForkSetting, "Yprofile-destination", "file", "Where to send profiling output - specify a file, default is to the console.", "", depends = List(YprofileEnabled -> true))
   val YprofileExternalTool: Setting[List[String]] = PhasesSetting(ForkSetting, "Yprofile-external-tool", "Enable profiling for a phase using an external tool hook. Generally only useful for a single phase.", "typer", depends = List(YprofileEnabled -> true))