test: fix parallel/test-tls-env-extra-ca.js

fix args in final assert.strictEqual() call

PR-URL: https://github.com/nodejs/node/pull/21647


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>