Update sbt-scalafmt to 2.5.6

Author: scala-steward

project/plugins.sbt

@@ -2,7 +2,7 @@ addSbtPlugin("com.github.sbt"                    % "sbt-pgp"            % "2.3.1
 addSbtPlugin("org.xerial.sbt"                    % "sbt-sonatype"       % "3.12.2")
 addSbtPlugin("com.thoughtworks.sbt-api-mappings" % "sbt-api-mappings"   % "3.0.2")
 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("org.scoverage"                     % "sbt-scoverage"      % "2.4.0")
 addSbtPlugin("org.scoverage"                     % "sbt-coveralls"      % "1.3.15")
 addSbtPlugin("com.typesafe"                      % "sbt-mima-plugin"    % "1.1.4")