Update sbt-pgp to 2.3.1

Author: scala-steward-bot

project/plugins.sbt

@@ -1,5 +1,5 @@
 scalacOptions ++= Seq("-unchecked", "-deprecation", "-feature")
 
 addSbtPlugin("org.xerial.sbt"   % "sbt-sonatype"    % "3.12.2")
-addSbtPlugin("com.github.sbt"     % "sbt-pgp"         % "2.3.0")
+addSbtPlugin("com.github.sbt"     % "sbt-pgp"         % "2.3.1")
 addSbtPlugin("org.scalariform"  % "sbt-scalariform" % "1.8.3")