doc: fix default encoding mention in crypto.md

The default encoding for crypto methods was changed in v6.0.0
with v4.x keeping a default of binary.

PR-URL: https://github.com/nodejs/node/pull/7805
Reviewed-By: Claudio Rodriguez <cjrodr@yahoo.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/crypto.md

@@ -913,7 +913,7 @@ recent OpenSSL releases, `openssl list-cipher-algorithms` will display the
 available cipher algorithms.
 
 The `key` is the raw key used by the `algorithm` and `iv` is an
-[initialization vector][]. Both arguments must be `'latin1'` encoded strings or
+[initialization vector][]. Both arguments must be `'utf8'` encoded strings or
 [buffers][`Buffer`].
 
 ### crypto.createCredentials(details)
@@ -968,7 +968,7 @@ recent OpenSSL releases, `openssl list-cipher-algorithms` will display the
 available cipher algorithms.
 
 The `key` is the raw key used by the `algorithm` and `iv` is an
-[initialization vector][]. Both arguments must be `'latin1'` encoded strings or
+[initialization vector][]. Both arguments must be `'utf8'` encoded strings or
 [buffers][`Buffer`].
 
 ### crypto.createDiffieHellman(prime[, prime_encoding][, generator][, generator_encoding])