test: fix missing param in benchmark-timers

When a new benchmark was added to timers, the test running these benchmarks was not updated to include the new n parameter.

Fixes: https://github.com/nodejs/node/issues/18730

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

test