CommonJS testing cycle uses stale data

In the process of generating a PR, I noticed that the GitHub test runners caught issues in `commonjs/{import_test.js,strict_test.js}` that weren't triggered by my local `gulp test_commonjs` runs. Closure tests did not seem to be impacted.

E.g. https://github.com/protocolbuffers/protobuf-javascript/actions/runs/3187010981/jobs/5198166279