Update sbt-dotty to 0.5.3 (#491)

Author: scala-steward

project/plugins.sbt

@@ -9,5 +9,5 @@ addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.0.0")
 addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "1.0.0")
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % scalaJSVersion)
 addSbtPlugin("org.scala-native" % "sbt-scala-native" % scalaNativeVersion)
-addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.5.2")
+addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.5.3")
 addSbtPlugin("de.heikoseeberger" % "sbt-header" % "5.6.0")