Oban: change :discard return values to :cancel

:discard will be removed in Oban 3.0. It was only meant for internal use.

lib/pleroma/workers/remote_fetcher_worker.ex

@@ -14,16 +14,16 @@ defmodule Pleroma.Workers.RemoteFetcherWorker do
         :ok
 
       {:rejected, reason} ->
-        {:discard, reason}
+        {:cancel, reason}
 
       {:error, :forbidden} ->
-        {:discard, :forbidden}
+        {:cancel, :forbidden}
 
       {:error, :not_found} ->
-        {:discard, :not_found}
+        {:cancel, :not_found}
 
       {:error, :allowed_depth} ->
-        {:discard, :allowed_depth}
+        {:cancel, :allowed_depth}
 
       {:error, _} = e ->
         e