doc: move reference to OpenSSL flags SSL_OP_*

Refs: https://github.com/nodejs/node/pull/34050

PR-URL: https://github.com/nodejs/node/pull/39935


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>