Don't expose binary format in preauth otp

(cherry picked from commit f2a177ddd2c4be7b2e2579a0bcd9d576a52ca216)

https://github.com/krb5/krb5/commit/47e4c8a5b638037f029a23129dc4ad344cf5b779
Author: Nathaniel McCallum <npmccallum@redhat.com>
Committer: Tom Yu <tlyu@mit.edu>
Commit: 47e4c8a5b638037f029a23129dc4ad344cf5b779
Branch: krb5-1.11
 src/include/krb5/krb5.hin      |    1 -
 src/lib/krb5/krb/preauth_otp.c |    3 ++-
 2 files changed, 2 insertions(+), 2 deletions(-)