Update sbt-scalajs, scalajs-compiler, ... to 1.20.2

Author: http4s-steward[bot]

project/plugins.sbt

@@ -1,6 +1,6 @@
 libraryDependencies += "org.scala-js" %% "scalajs-env-selenium" % "1.1.1"
 
 addSbtPlugin("org.http4s" % "sbt-http4s-org" % "2.0.0")
-addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.19.0")
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.20.2")
 addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.11.0")
 addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.5.8")