Update sbt-mdoc to 2.3.6 (#2813)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: scala-steward

project/plugins.sbt

@@ -18,7 +18,7 @@ addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.15")
 
 addSbtPlugin("com.thoughtworks.sbt-api-mappings" % "sbt-api-mappings" % "3.0.2")
 
-addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.3.2")
+addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.3.6")
 
 addSbtPlugin("com.eed3si9n" % "sbt-sriracha" % "0.1.0")