Update sbt-scalafmt to 2.5.6

Author: scala-steward

modules/core/src/test/scala/org/scalasteward/core/edit/update/VersionPositionScannerTest.scala

@@ -67,7 +67,7 @@ class VersionPositionScannerTest extends FunSuite {
     val d = "org.scala-js".g % "sbt-scalajs".a % "0.6.23"
     val fd = FileData(
       "plugins.sbt",
-      s"""addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.5")
+      s"""addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.6")
          |addSbtPlugin("${d.groupId}" % "${d.artifactId.name}" % "${d.version}")
          |addSbtPlugin("org.scoverage" % "sbt-scoverage" % "2.2.0")""".stripMargin
     )

project/plugins.sbt

@@ -1,7 +1,7 @@
 addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "2.3.1")
 addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.13.1")
 addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.11.2")
-addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.5")
+addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.6")
 addSbtPlugin("com.github.cb372" % "sbt-explicit-dependencies" % "0.3.1")
 addSbtPlugin("io.github.sbt-doctest" % "sbt-doctest" % "0.12.2")
 addSbtPlugin("com.github.sbt" % "sbt-native-packager" % "1.11.4")