Update sbt-scalafmt to 2.5.4 (#661)

Author: scala-steward

project/plugins.sbt

@@ -6,7 +6,7 @@ addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "1.3.2")
 
 addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.9.2")
 
-addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.2")
+addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.4")
 
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.13.0")