Revert "Remove sbt-dotty from generated plugins file"

This reverts commit 2f16b32.

Author: armanbilge

project/Build.scala

@@ -1616,6 +1616,7 @@ object Build {
         // (publishLocal in `scala3-staging`).value
         val pluginText =
           s"""updateOptions in Global ~= (_.withLatestSnapshots(false))
+             |addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "$sbtDottyVersion")
              |addSbtPlugin("ch.epfl.lamp" % "sbt-community-build" % "$sbtCommunityBuildVersion")
              |addSbtPlugin("org.scala-js" % "sbt-scalajs" % "$scalaJSVersion")""".stripMargin
         IO.write(baseDirectory.value / "sbt-dotty-sbt", pluginText)