Update sbt-ci-release to 1.6.0 (#409)

Author: scala-steward

project/plugins.sbt

@@ -2,7 +2,7 @@ val Dependencies = new {
   val Versions = new {
     val missinglink = "0.2.11"
     val sbtBuildinfo = "0.12.0"
-    val sbtCiRelease = "1.5.12"
+    val sbtCiRelease = "1.6.0"
     val sbtMissinglink = "0.3.6"
     val sbtRewarn = "0.1.3"
     val sbtScalafmt = "2.5.2"