Fix typo in install_kdc.rst

(cherry picked from commit f619c2621443d9463898c434828dc67e587c2afd)

https://github.com/krb5/krb5/commit/668e0610496f190fbdf892b2ceb944e6dc0048d7
Author: Greg Hudson <ghudson@mit.edu>
Committer: Tom Yu <tlyu@mit.edu>
Commit: 668e0610496f190fbdf892b2ceb944e6dc0048d7
Branch: krb5-1.14
 doc/admin/install_kdc.rst |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)