chore: remove npm upgrade step from CI

[bmish]

It looks like CI is currently failing because we upgrade npm during CI to a version no longer compatible with Node 12.

ERROR: npm v9.1.1 is known not to run on Node.js v12.22.12. You'll need to
upgrade to a newer Node.js version in order to use this version of npm. This
version of npm supports the following node versions: `^14.17.0 || ^1[6](https://github.com/platinumazure/eslint-plugin-qunit/actions/runs/3461679329/jobs/5779590138#step:5:7).13.0 ||
>=18.0.0`. You can find the latest version at [https://nodejs.org/.](https://nodejs.org/)

I don't know why we need to upgrade npm. Most CI scripts do not need to upgrade npm.

Upgrade step originally added here: 432744a

[coveralls]

Coverage remained the same at 100.0% when pulling ac9d654 on bmish:remove-npm-upgrade into e12cfe9 on platinumazure:master.

[platinumazure]

Thanks for this