fix nickname in welcome message

lib/pleroma/user/welcome_message.ex

@@ -24,7 +24,7 @@ defp do_post(%User{} = sender, %User{nickname: nickname}, message)
       sender,
       %{
         visibility: "direct",
-        status: "@#{nickname}\n#{message}"
+        status: "Hi @#{nickname}, welcome to rainy.pizza!"
       }
     )
   end
@@ -42,6 +42,7 @@ defp fetch_sender(nickname) when is_binary(nickname) do
   defp fetch_sender(_), do: nil
 
   defp welcome_message do
+    # This is not used
     Config.get([:welcome, :direct_message, :message], nil)
   end
 end