Update sbt-ci-release to 1.9.3 (#125)

Author: scala-steward

project/plugins.sbt

@@ -1,4 +1,4 @@
 addSbtPlugin("org.portable-scala" % "sbt-scala-native-crossproject" % "1.3.2")
 addSbtPlugin("org.scala-native" % "sbt-scala-native" % "0.5.7")
 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" % "1.9.3")