core: Don't report error on setting option 'allow-emacs-pinentry'.
Previously "OPTION allow-emacs-pinentry" returned an error if the Emacs
pinentry is not compiled in. Since it is merely an option, it would
make more sense to just return OK.
- Suggested-by: Werner Koch <wk@gnupg.org>
- Signed-off-by: Daiki Ueno <ueno@gnu.org>