Update sbt-mdoc to 2.2.2 (#125)

Author: scala-steward

project/plugins.sbt

@@ -4,7 +4,7 @@ addSbtPlugin("se.marcuslonnberg"    % "sbt-docker"               % "1.5.0")
 addSbtPlugin("com.eed3si9n"         % "sbt-buildinfo"            % "0.9.0")
 addSbtPlugin("com.geirsson"         % "sbt-ci-release"           % "1.5.3")
 addSbtPlugin("org.scalameta"        % "sbt-scalafmt"             % "2.4.0")
-addSbtPlugin("org.scalameta"        % "sbt-mdoc"                 % "2.1.5")
+addSbtPlugin("org.scalameta"        % "sbt-mdoc"                 % "2.2.2")
 addSbtPlugin("de.heikoseeberger"    % "sbt-header"               % "5.6.0")
 addSbtPlugin("com.alejandrohdezma" %% "sbt-github"               % "0.8.2")
 addSbtPlugin("com.alejandrohdezma"  % "sbt-github-header"        % "0.8.2")