aklog: Fix allow_weak_crypto warning

It's _crypto, not _enctypes. The user will just be more confused than
before if we tell them to do the wrong thing.

Change-Id: Ib94b14efbd3c89d9f58fb8985326ee8691fd993b
Reviewed-on: http://gerrit.openafs.org/8938
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Simon Wilkinson <simonxwilkinson@gmail.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>