Add "Kerberos" to PDF titles

(cherry picked from commit 703ee0a74900d9acb8dd48f60149a34e1b7411a8)

https://github.com/krb5/krb5/commit/c911f51ac81ff16ab0d3b271460cccb6bcb60275
Author: Tom Yu <tlyu@mit.edu>
Commit: c911f51ac81ff16ab0d3b271460cccb6bcb60275
Branch: krb5-1.11
 doc/conf.py |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)