scd: Fix detecting digest OID in the message to be signed.
* scd/app-openpgp.c (do_auth): Don't exclude Ed25519 for removing digest OID.
- GnuPG-bug-id: T7589
- Fixes-commit: 3132bd90dc8db9c7fd19ba201918e95891306dc5
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>