Merge pull request #271 from scala-steward/update/2.2.x/sbt-ci-release-1.9.0

[2.2.x] sbt-ci-release 1.9.0 (was 1.6.1)

Author: mkurz

project/plugins.sbt

@@ -1,3 +1,3 @@
 addSbtPlugin("com.typesafe.play" % "sbt-twirl"      % "1.6.8")
 addSbtPlugin("org.scalameta"     % "sbt-scalafmt"   % "2.5.2")
-addSbtPlugin("com.github.sbt"    % "sbt-ci-release" % "1.6.1")
+addSbtPlugin("com.github.sbt"    % "sbt-ci-release" % "1.9.0")