Update sbt-dotty to 0.5.0 (#400)

Author: scala-steward

project/plugins.sbt

@@ -4,7 +4,7 @@ val scalaJSVersion =
 val scalaNativeVersion =
   Option(System.getenv("SCALANATIVE_VERSION")).filter(_.nonEmpty).getOrElse("0.3.9")
 
-addSbtPlugin("ch.epfl.lamp"           % "sbt-dotty"                     % "0.4.6")
+addSbtPlugin("ch.epfl.lamp"           % "sbt-dotty"                     % "0.5.0")
 addSbtPlugin("org.scala-js"           % "sbt-scalajs"                   % scalaJSVersion)
 addSbtPlugin("org.portable-scala"     % "sbt-scalajs-crossproject"      % crossVer)
 addSbtPlugin("org.scala-native"       % "sbt-scala-native"              % scalaNativeVersion)