Fix typo in enctypes.rst

(cherry picked from commit 61375be10beed5e95ea241e22fc580483caabf52)

https://github.com/krb5/krb5/commit/d9a11cf45ce526fbd79c54821ec9a11b07e30231
Author: Weijun Wang <weijun.wang@oracle.com>
Committer: Greg Hudson <ghudson@mit.edu>
Commit: d9a11cf45ce526fbd79c54821ec9a11b07e30231
Branch: krb5-1.19
 doc/admin/enctypes.rst |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)