Update sbt-header to 5.7.0 (#29)

Author: scala-steward

project/plugins.sbt

@@ -16,4 +16,4 @@ addSbtPlugin("com.eed3si9n"       % "sbt-buildinfo"                 % "0.11.0")
 addSbtPlugin("com.github.sbt"       % "sbt-pgp"                       % "2.1.2")
 addSbtPlugin("org.xerial.sbt"     % "sbt-sonatype"                  % "3.9.12")
 addSbtPlugin("com.dwijnand"       % "sbt-dynver"                    % "4.1.1")
-addSbtPlugin("de.heikoseeberger"  % "sbt-header"                    % "5.6.5")
+addSbtPlugin("de.heikoseeberger"  % "sbt-header"                    % "5.7.0")