I had tried earlier to remove this attribute in the conventional manner, but failed.
[root@ef-idm01 ~]#
ipa -e in_server=true user-mod waynev --delattr=krblastadminunlock=20171006230951Z
ipa: ERROR: krblastadminunlock does not contain '20171006230951Z'
grant@ef-idm01:~[20221123-6:59][#1012]$
klist
Ticket cache: KEYRING:persistent:555:555
Valid starting Expires Service principal
grant@ef-idm01:~[20221123-6:59][#1013]$
ipa user-mod --delattr=krblastadminunlock=20171006230951Z waynev
ipa: ERROR: krblastadminunlock does not contain '20171006230951Z'
grant@ef-idm01:~[20221123-6:59][#1014]$
ipa user-show --all waynev | grep krblastadminunlock
krblastadminunlock: 20171006230951Z
grant@ef-idm01:~[20221123-DING!][#1015]$