[app-crypt/qca] Correct plugin path to upstream changes

See: http://quickgit.kde.org/?p=qca.git&a=commitdiff&h=192243d4bdafddf38dd7a7b508524ee5cb1ecdb5&hp=2950458c77928bf0f096e61f5a069bdb2862665e

Package-Manager: portage-2.2.12