test: removing unnecessary parameter from assert call

Removed unnecessary parameter from assert call in
test/parallel/test-stream2-basic.js.

Fixes: https://github.com/nodejs/node/issues/21305

PR-URL: https://github.com/nodejs/node/pull/21307


Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>