gpg: Un-deprecate option --auto-key-retrieve.

* g10/gpg.c (main): Remove deprecation warning.

Most options for the keyserver have been moved to dirmngr and thus it
does not make sense to favor "--keyserver-options auto-key-retrieve"
over the direct options --auto-key-retrieve and --no-auto-key-retrieve.

• Signed-off-by: Werner Koch <wk@gnupg.org>