Add deprecation notice

files/gitlab-cookbooks/package/libraries/deprecations.rb

@@ -71,6 +71,12 @@ module Gitlab
             deprecation: '13.3',
             removal: '14.0',
             note: "Geo does not require Foreign Data Wrapper (FDW) to be configured to replicate data."
+          },
+          {
+            config_keys: %w(praefect virtual_storages primary),
+            deprecation: '13.3',
+            removal: '13.4',
+            note: "Praefect no longer supports statically designating primary Gitaly nodes."
           }
         ]