Update sbt-ci-release to 1.9.3

Author: scala-steward

Diff for: project/plugins.sbt

@@ -6,4 +6,4 @@ addSbtPlugin("com.typesafe.sbt" % "sbt-site" % "1.4.1")
 addSbtPlugin("org.scoverage" % "sbt-coveralls" % "1.3.15")
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.4")
 addSbtPlugin("org.scoverage" % "sbt-scoverage" % "2.0.0")
-addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.10")
+addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.9.3")