Merge pull request #4586 from typelevel/update/series/3.x/sbt-mdoc-2.9.0

Update sbt-mdoc to 2.9.0 in series/3.x

Author: djspiewak

project/plugins.sbt

@@ -5,7 +5,7 @@ addSbtPlugin("org.typelevel" % "sbt-typelevel" % "0.8.5")
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.21.0")
 addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.5.11")
 addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.4.8")
-addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.8.2")
+addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.9.0")
 addSbtPlugin("com.lightbend.sbt" % "sbt-java-formatter" % "0.8.0")
 addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.13.1")
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.14.6")