Do not include hidden files in the sidebar

We play games with hidden toctrees in the RST source to avoid
Sphinx warnings; make sure that they do not affect the rendered
output.

(cherry picked from commit b017751b711dfd70c8735f655a51e5ff860af49b)

https://github.com/krb5/krb5/commit/77f65c991e945e5e33008345d17ae04bebc5c824
Author: Ben Kaduk <kaduk@mit.edu>
Committer: Tom Yu <tlyu@mit.edu>
Commit: 77f65c991e945e5e33008345d17ae04bebc5c824
Branch: krb5-1.11
 doc/_templates/layout.html |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)