gpg: Make --skip-hidden-recipients work again.
* g10/pubkey-enc.c (get_session_key): Take care of opt.skip_hidden_recipients.
This was lost due to
- Fixes-commit: ce2f71760155b71a71418fe145a557c99bd52290
- GnuPG-bug-id: T4169
- Signed-off-by: Werner Koch <wk@gnupg.org>