Update sbt-unidoc to 0.6.1 (#430)

Co-authored-by: foldl <sagi.fogel@gmail.com>

Author: scala-steward

project/plugins.sbt

@@ -1,5 +1,5 @@
 addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.3.8")
-addSbtPlugin("com.github.sbt" % "sbt-unidoc" % "0.6.0")
+addSbtPlugin("com.github.sbt" % "sbt-unidoc" % "0.6.1")
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.20.2")
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.6")
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.11.1")