This is needed to update net/rubygem-net-ldap.
Entries in the redmine issue tracker and experience in the Foreman and Katello projects with the ldap_fluff gem suggest that this is safe to go, but I don't have a redmine with LDAP to actually test this.
Proposed commit message:

www/redmine: allow newer net-ldap versions

Approved by:	swills (mentor), mat (mentor)

poudriere: http://space.kvedulv.de/FreeBSD/redmine-2.6.3_2.log
portlint:

mmoll@marduk:/svn/ports/www/redmine$ portlint -ACNc
WARN: Makefile: new ports should not set PORTREVISION.
0 fatal errors and 1 warning found.