Update sbt-pgp to 2.2.1 (#176)

Author: scala-steward

project/plugins.sbt

@@ -1,4 +1,4 @@
 addSbtPlugin("com.github.sbt" % "sbt-native-packager" % "1.9.16")
 addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.11.0")
 addSbtPlugin("com.github.sbt" % "sbt-git" % "2.0.0")
-addSbtPlugin("com.github.sbt" % "sbt-pgp" % "2.1.2")
+addSbtPlugin("com.github.sbt" % "sbt-pgp" % "2.2.1")