Update sbt-pgp to 2.2.1

Author: scala-steward

project/plugins.sbt

@@ -1,4 +1,4 @@
 addSbtPlugin("com.timushev.sbt" % "sbt-updates"  % "0.6.2")
 addSbtPlugin("org.xerial.sbt"   % "sbt-sonatype" % "3.9.13")
-addSbtPlugin("com.github.sbt"   % "sbt-pgp"      % "2.1.2")
+addSbtPlugin("com.github.sbt"   % "sbt-pgp"      % "2.2.1")
 addSbtPlugin("org.scalameta"    % "sbt-scalafmt" % "2.4.6")