Update sbt-scalafix to 0.12.1 (#617)

Author: scala-steward

project/plugins.sbt

@@ -8,7 +8,7 @@ addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.12")
 
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.2")
 
-addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.12.0")
+addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.12.1")
 
 addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.12.0")