doc: remove invalid padding from privateEncrypt

PR-URL: https://github.com/nodejs/node/pull/9611
Fixes: https://github.com/nodejs/node/issues/9609
Reviewed-By: Claudio Rodriguez <cjrodr@yahoo.com>
Reviewed-By: Sam Roberts <sam@strongloop.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

doc/api/crypto.md

@@ -1405,7 +1405,6 @@ keys:
 * `padding` : An optional padding value, one of the following:
   * `constants.RSA_NO_PADDING`
   * `constants.RSA_PKCS1_PADDING`
-  * `constants.RSA_PKCS1_OAEP_PADDING`
 
 All paddings are defined in the `constants` module.