test: remove timers from streams test

test-stream2-readable-empty-buffer-no-eof fails on resource-constrained
machines due to its use of timers. Removing timers makes it more
reliable and doesn’t affect the validity of the test, as it only uses
relative timing relations.

Failures were noticed on freebsd10-64 in CI. I am able to replicate the
failure with `tools/test.py --repeat=100 -j 100`. When run alone, it
passes reliably.

Refs: https://github.com/nodejs/node/pull/9359
PR-URL: hkttps://github.com/nodejs/node/pull/9360


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>