ref(node): Remove duplicate function `isCjs`

[github-actions]

Note

The pull request "ref(node): Remove duplicate function isCjs" was created by @s1gr1d but did not reference an issue. Therefore this issue was created for better visibility in external tools like Linear.

While working on something else I stumbled over this unused, duplicated function. Also, there was still one implementation in Google Cloud Serverless, which checked for typeof require !== 'undefined', which does not work well all the time (see this PR: #15927).

[linear]

JS-1382

[github-actions]

A PR closing this issue has just been released 🚀

This issue was referenced by PR #18662, which was included in the 10.33.0 release.