Backport "pull request automation use regular npm install"

[getdave]

What?

Backport of #66314.

Why?

Because CI is failing npm install on the wp/6.7 branch.

See discussion in WP Slack https://wordpress.slack.com/archives/C02QB2JS7/p1729680379803689.

How?

Manual backport.

Testing Instructions

Deferring to @sirreal to double check this makes sense.

Testing Instructions for Keyboard

Screenshots or screencast

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[sirreal]

This looks correct to me 👍

Other release branches may experience the same issue.

This workflow was fragile because it was effectively configured on one commit in a way that relied on the state of the repo in another commit. This change should make it less fragile.

[sirreal]

Strange. That error on CI is exactly what was observed previously that was fixed by the same change in #66314.

I'll investigate soon…

[kevin940726]

The failing workflow is running on the pull_request_target event.

This event runs in the context of the base of the pull request, rather than in the context of the merge commit, as the pull_request event does.

That is, the workflow is still the old one on wp/6.7, not the updated one in this PR. I think the failure is expected. We might just have to merge this to see if it works.

[sirreal]

Good spot @kevin940726, that would explain why this fix didn't work on the branch 🙂

I maintain that this change should be merged to wp/6.7 to fix the issue 👍

[sirreal]

This was tested with #66457 and it seemed to work correctly.