Update sbt-mdoc to 2.6.5 (#300)

Author: softwaremill-ci

project/plugins.sbt

@@ -1,4 +1,4 @@
 val sbtSoftwareMillVersion = "2.0.25"
 addSbtPlugin("com.softwaremill.sbt-softwaremill" % "sbt-softwaremill-common" % sbtSoftwareMillVersion)
 addSbtPlugin("com.softwaremill.sbt-softwaremill" % "sbt-softwaremill-publish" % sbtSoftwareMillVersion)
-addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.6.4")
+addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.6.5")