Update sbt-ci-release to 1.5.9 (#380)

Author: scala-steward

Diff for: project/plugins.sbt

@@ -1,6 +1,6 @@
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.7.0")
 addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.1.0")
-addSbtPlugin("com.geirsson" % "sbt-ci-release" % "1.5.7")
+addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.9")
 
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.4.3")