Update sbt-ci-release to 1.8.0 (#406)

Author: scala-steward

project/plugins.sbt

@@ -1,6 +1,6 @@
 addSbtPlugin("com.github.sbt" % "sbt-pgp" % "2.3.0")
 
-addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.7.0")
+addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.8.0")
 
 addSbtPlugin("com.thesamet" % "sbt-protoc" % "1.0.7")