Update sbt-ci-release to 1.5.12 (#260)

Author: scala-steward

project/plugins.sbt

@@ -1,4 +1,4 @@
 libraryDependencies += "org.scala-sbt" % "scripted-plugin_2.12" % sbtVersion.value
 
-addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.11")
+addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.12")
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.0")