test: update test-timers-block-eventloop.js
When CPU is busy, the above sequential case fails occasionally, expand the timeout value to fix it.
Fixes: https://github.com/nodejs/node/issues/16310
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines