Update mdoc, sbt-mdoc to 2.8.0

Author: scala-center-steward[bot]

project/plugins.sbt

@@ -2,7 +2,7 @@ addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.11.2")
 addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.13.1")
 addSbtPlugin("com.github.sbt" % "sbt-ghpages" % "0.9.0")
 addSbtPlugin("ch.epfl.scala" % "sbt-version-policy" % "3.2.1")
-addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.7.2")
+addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.8.0")
 addSbtPlugin("org.scoverage" % "sbt-scoverage" % "2.4.1")
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.14.4")
 addSbtPlugin("com.eed3si9n" % "sbt-projectmatrix" % "0.11.0")