doc: fix typo for `decipher.final`.

The `output_encoding` parameter should be as the same as
`decipher.update`.

PR-URL: https://github.com/nodejs/node/pull/10086
Reviewed-By: Anna Henningsen <anna@addaleax.net>

doc/api/crypto.md

@@ -313,7 +313,7 @@ added: v0.1.94
 -->
 
 Returns any remaining deciphered contents. If `output_encoding`
-parameter is one of `'latin1'`, `'base64'` or `'hex'`, a string is returned.
+parameter is one of `'latin1'`, `'ascii'` or `'utf8'`, a string is returned.
 If an `output_encoding` is not provided, a [`Buffer`][] is returned.
 
 Once the `decipher.final()` method has been called, the `Decipher` object can