constants: add as_public constant and use it everywhere

lib/mix/tasks/pleroma/database.ex

@@ -8,6 +8,7 @@ defmodule Mix.Tasks.Pleroma.Database do
   alias Pleroma.Repo
   alias Pleroma.User
   require Logger
+  require Pleroma.Constants
   import Mix.Pleroma
   use Mix.Task
 
@@ -99,10 +100,15 @@ defmodule Mix.Tasks.Pleroma.Database do
       NaiveDateTime.utc_now()
       |> NaiveDateTime.add(-(deadline * 86_400))
 
-    public = "https://www.w3.org/ns/activitystreams#Public"
-
     from(o in Object,
-      where: fragment("?->'to' \\? ? OR ?->'cc' \\? ?", o.data, ^public, o.data, ^public),
+      where:
+        fragment(
+          "?->'to' \\? ? OR ?->'cc' \\? ?",
+          o.data,
+          ^Pleroma.Constants.as_public(),
+          o.data,
+          ^Pleroma.Constants.as_public()
+        ),
       where: o.inserted_at < ^time_deadline,
       where:
         fragment("split_part(?->>'actor', '/', 3) != ?", o.data, ^Pleroma.Web.Endpoint.host())