doc: fix echo example programs

Adjust to work with self-signed certificates, and certificates that do
not name "localhost" as their host name.
Removed duplicate examples, they differed only by using `pfx`. Its not
necessary to show every option, and we don't, and the example wouldn't
work with most pfx anyway, since it didn't specify a password.

PR-URL: https://github.com/nodejs/node/pull/24235


Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>