test: deflake test-tls-passphrase

Move `socket.end()` to client.

Fixes: https://github.com/nodejs/node/issues/28111
Refs: https://github.com/nodejs/node/pull/27569

PR-URL: https://github.com/nodejs/node/pull/29134


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>