test: fix conversion of microseconds in test

[nickstanish]

Fixes: #8728

Changes the conversion for process cpuUsage test

Checklist

• commit message follows commit guidelines

Affected core subsystem(s)

process

[Trott]

LGTM.

[Trott]

Hi, @nickstanish! Welcome, and thanks for the contribution!

Small change to the commit message (and I guess this PR title too): The subsystem here is test rather than process. So that should be the first word (before the colon) of the commit message and PR title. No big deal if it doesn't happen--whoever lands the PR can do it, but if you want to save them a few keystrokes, that would be great.

[Trott]

Pummel tests don't get run in Ci so only the linter results are relevant, but here's a CI run anyway...

CI: https://ci.nodejs.org/job/node-test-pull-request/9565/

CI has not been having a good week, but we should be able to get some linter results at least. :-D

[pmuellr]

thanks @nickstanish !!! LGTM

[Trott]

CI is good (only failure is a known issue unrelated to this).

Given the small nature of the change, the low risk (it's a test modification, and easy to revert if it turns out there is an unforeseen problem), and the copious approvals, I'm going to land this now rather than waiting the full 48 hours.

[Trott]

Landed in a439cf4.

Thanks for the contribution! 🎉