Merge pull request #517 from scala-steward/update/3.0.x/sbt-scalafmt-2.6.0

[3.0.x] sbt-scalafmt 2.6.0 (was 2.5.6)

Author: mkurz

project/plugins.sbt

@@ -1,5 +1,5 @@
 addSbtPlugin("com.typesafe"   % "sbt-mima-plugin"    % "1.1.5")
 addSbtPlugin("com.github.sbt" % "sbt-java-formatter" % "0.11.0")
 addSbtPlugin("com.github.sbt" % "sbt-header"         % "5.11.0")
-addSbtPlugin("org.scalameta"  % "sbt-scalafmt"       % "2.5.6")
+addSbtPlugin("org.scalameta"  % "sbt-scalafmt"       % "2.6.0")
 addSbtPlugin("com.github.sbt" % "sbt-ci-release"     % "1.11.2")