Fix typo in manual page
Fix typo in manual page

Thanks Benedict Reuschling for pointing this out.

Closes https://github.com/arthurdejong/nss-pam-ldapd/issues/39
Fixes b93838d

arthurdejong/nss-pam-ldapd,arthurdejong/nss-pam-ldapd,arthurdejong/nss-pam-ldapd