mail/claws-mail: Link with net/openldap26-client if installed.

Reported by: Ivan Rozhuk <rozhuk.im@gmail.com>
PR: 274190
MFH: 2024Q1

(cherry picked from commit ae03dfaa96e334b41d1f41297aadd99508fc0f49)

This commit does not contain the switch to share/man for manpages.