gpg: Remove unused function get_pubkeys.

* g10/getkey.c (get_pubkeys): Remove.
(pubkey_free): Remove and use code directly ...
(pubkeys_free): ... here.

(cherry picked from commit ed8fe21e6612401846fc4af8631f0136dc633c67)

• Signed-off-by: Werner Koch <wk@gnupg.org>