Merge pull request #500 from scala-steward/update/7.x/sbt-ci-release-1.9.0

[7.x] sbt-ci-release 1.9.0 (was 1.8.0)

Author: mkurz

project/plugins.sbt

@@ -6,6 +6,6 @@ addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "1.1.4")
 
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.2")
 
-addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.8.0")
+addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.9.0")
 
 addSbtPlugin("com.lightbend.sbt" % "sbt-java-formatter" % "0.8.0")