Fix anchoring in postgresql::server::plperl

When using anchors, resources should be sandwiched those. An ordering
relation was missing for the "end" anchor.

manifests/server/plperl.pp

@@ -16,5 +16,5 @@
   -> Class['postgresql::server::install']
   -> Package['postgresql-plperl']
   -> Class['postgresql::server::service']
-  anchor { 'postgresql::server::plperl::end': }
+  -> anchor { 'postgresql::server::plperl::end': }
 }