Update sbt-typelevel, sbt-typelevel-site to 0.4.20

Author: datahub-rewrite-bot

project/plugins.sbt

@@ -1,4 +1,4 @@
-addSbtPlugin("org.typelevel" % "sbt-typelevel" % "0.4.19")
-addSbtPlugin("org.typelevel" % "sbt-typelevel-site" % "0.4.19")
+addSbtPlugin("org.typelevel" % "sbt-typelevel" % "0.4.20")
+addSbtPlugin("org.typelevel" % "sbt-typelevel-site" % "0.4.20")
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.13.0")
 addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.3.7")