Update sbt-pgp to 2.1.1 (#73)

Author: scala-steward

project/plugins.sbt

@@ -1,5 +1,5 @@
 addSbtPlugin("com.github.gseitz" % "sbt-release" % "1.0.13")
 
-addSbtPlugin("com.jsuereth" % "sbt-pgp" % "2.0.2")
+addSbtPlugin("com.jsuereth" % "sbt-pgp" % "2.1.1")
 
 addSbtPlugin("org.scoverage" % "sbt-scoverage" % "1.6.1")