doc: new TLSSocket has no secure context options

Unlike all the other tls APIs, if any secure context configuration is
required, the caller is responsible for creating the context.

Corrects a doc regression introduced in caa7fa98.

PR-URL: https://github.com/nodejs/node/pull/10545


Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>