Update sbt-scalafix to 0.13.0 (#879)

Author: scala-steward

project/plugins.sbt

@@ -4,7 +4,7 @@ addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.6.1")
 addSbtPlugin("com.eed3si9n"   % "sbt-assembly"   % "0.14.10")
 addSbtPlugin("org.scalameta"  % "sbt-scalafmt"   % "2.5.2")
 addSbtPlugin("org.scoverage"  % "sbt-scoverage"  % "2.2.1")
-addSbtPlugin("ch.epfl.scala"  % "sbt-scalafix"   % "0.12.1")
+addSbtPlugin("ch.epfl.scala"  % "sbt-scalafix"   % "0.13.0")
 
 if (System.getProperty("add-scapegoat-plugin") == "true")
   addSbtPlugin(s"com.sksamuel.scapegoat" % "sbt-scapegoat" % "1.1.0")