/etc/xdg/kldap.categories is in kio-ldap 17.12.3-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2
org.kde.pim.kldap kioslave (kldap) org.kde.pim.ldap kldaplib (kldap)