core: Make sure the keygrip is available in WITH_SECRET mode.

* src/engine-gpg.c (gpg_keylist_build_options): Send --with-keygrip
if --with-secret is used.

Since GnuPG 2.2.19 the keygrip was not anymore send if only
--with-secret was used in a public key listing. Given that
--with-secret requires computation of the keygrip anyway, there is no
point in not requesting the keyrip in this case.

• GnuPG-bug-id: T4820