test: remove node-tap lookalike

This commit removes the small node-tap lookalike from several
of the streams2 tests. It's only used by six tests, and is
inconsistent with all other tests.

Backport-PR-URL: #17024
PR-URL: #13707
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: cjihrig