Merge pull request #1275 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.eed3si9n"       % "sbt-assembly"    % "2.1.5")
-addSbtPlugin("org.scalameta"      % "sbt-scalafmt"    % "2.5.6")
+addSbtPlugin("org.scalameta"      % "sbt-scalafmt"    % "2.6.0")
 addSbtPlugin("com.typesafe"       % "sbt-mima-plugin" % "1.1.5")
 addSbtPlugin("com.github.sbt"     % "sbt-header"      % "5.11.0")
 addSbtPlugin("pl.project13.scala" % "sbt-jmh"         % "0.4.8")