Update sbt-pgp to 2.3.1

Author: scala-steward

project/Plugins.sbt

@@ -1,4 +1,4 @@
 addSbtPlugin("org.xerial.sbt" % "sbt-sonatype" % "2.3")
-addSbtPlugin("com.github.sbt" % "sbt-pgp" % "2.3.0")
+addSbtPlugin("com.github.sbt" % "sbt-pgp" % "2.3.1")
 addSbtPlugin("com.github.sbt" % "sbt-release" % "1.1.0")
 addSbtPlugin("org.scalastyle" %% "scalastyle-sbt-plugin" % "1.0.0")