Update sbt-ci-release to 1.5.7 (#19)

Author: scala-steward

project/plugins.sbt

@@ -2,7 +2,7 @@
 resolvers += Resolver.sonatypeRepo("snapshots")
 
 // includes sbt-dynver sbt-pgp sbt-sonatype sbt-git
-addSbtPlugin("com.geirsson" % "sbt-ci-release"  % "1.5.6")
+addSbtPlugin("com.geirsson" % "sbt-ci-release"  % "1.5.7")
 addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.8.1")
 
 // Scala Native support