Update sbt-scalafmt to 2.6.1

Author: mkurz

project/plugins.sbt

@@ -1,3 +1,3 @@
 addSbtPlugin("com.github.sbt" % "sbt-ci-release"     % "1.11.2")
 addSbtPlugin("com.github.sbt" % "sbt-github-actions" % "0.30.0")
-addSbtPlugin("org.scalameta"  % "sbt-scalafmt"       % "2.6.0")
+addSbtPlugin("org.scalameta"  % "sbt-scalafmt"       % "2.6.1")