Fix h1 end tag in Sphinx header titles

A </h1> end tag was incorrectly written as <h1>.  Also adjust style
settings so that the resulting computed style remains the same for
div.rel.

(cherry picked from commit 21e14aed841e109b31a9f27c0e78751e450364f2)

https://github.com/krb5/krb5/commit/07bccd65bb60986f1bf5ac0f9de29805cd270fae
Author: Tom Yu <tlyu@mit.edu>
Commit: 07bccd65bb60986f1bf5ac0f9de29805cd270fae
Branch: krb5-1.11
 doc/_static/kerb.css       |    6 ++++++
 doc/_templates/layout.html |    4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)