Fix ebn issues in documentation
Summary: See http://ebn.kde.org/sanitizer/reports/kde-4.x/applications/khelpcenter/index.html
Test Plan: meinproc5 index.docbook works
Reviewers: Documentation, yurchor, ltoscano
Reviewed By: Documentation, yurchor, ltoscano
Subscribers: ltoscano, yurchor, kde-doc-english
Tags: Documentation
Differential Revision: https://phabricator.kde.org/D27546