dirmngr: Emit correct spelling of "superseded".

* dirmngr/crlcache.c (list_one_crl_entry): Spell superseded correctly.
* dirmngr/ocsp.c (ocsp_invalid): Likewise.

This might break some tools which parse the existing output and expect
misspellings, but i'm not sure there are many such tools, and we
should use standardized orthography going forward.

• Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>