Fix typo: s/"tags"/"tag"/g

lib/pleroma/web/activity_pub/mrf/simple_policy.ex

@@ -55,7 +55,7 @@ defmodule Pleroma.Web.ActivityPub.MRF.SimplePolicy do
     object =
       if Enum.member?(Pleroma.Config.get([:mrf_simple, :media_nsfw]), actor_host) do
         tags = (child_object["tag"] || []) ++ ["nsfw"]
-        child_object = Map.put(child_object, "tags", tags)
+        child_object = Map.put(child_object, "tag", tags)
         child_object = Map.put(child_object, "sensitive", true)
         Map.put(object, "object", child_object)
       else

lib/pleroma/web/activity_pub/mrf/tag_policy.ex

@@ -31,7 +31,7 @@ defmodule Pleroma.Web.ActivityPub.MRF.TagPolicy do
 
     object =
       object
-      |> Map.put("tags", tags)
+      |> Map.put("tag", tags)
       |> Map.put("sensitive", true)
 
     message = Map.put(message, "object", object)