[InterNetNews/inn] 721e58: Improve actsync documentation

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: 721e58ddda3dbeb8b4fb2e5eda06ebc48668c41c
      https://github.com/InterNetNews/inn/commit/721e58ddda3dbeb8b4fb2e5eda06ebc48668c41c
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2022-02-05 (Sat, 05 Feb 2022)

  Changed paths:
    M doc/pod/actsync.pod

  Log Message:
  -----------
  Improve actsync documentation

Add a new section at the beginning to summarize how to use actsyncd.

Document that debug-level option is not possible for FTP retrieval.

Change news.uu.net to news.server.com out of clarity.  There's no official
news server to synchronize from.