Merge pull request #205 from scala-steward/update/sbt-mdoc-2.2.21

Update sbt-mdoc to 2.2.21

Author: EmergentOrder

project/plugins.sbt

@@ -6,7 +6,7 @@ addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.27")
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" %  "2.4.2")
 addSbtPlugin("org.xerial.sbt" % "sbt-sonatype" % "3.9.7")
 addSbtPlugin("com.github.sbt" % "sbt-pgp" % "2.1.2")
-addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.2.20" )
+addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.2.21" )
 addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler" % "0.20.0") // "0.21.0-RC1")
 // for Scala.js 1.x.x
 addSbtPlugin("org.scalablytyped.converter" % "sbt-converter" % "1.0.0-beta32")