remove automatic building in favor of just testing build completion

[bmos]

The build/test action was failing for new PRs and new releases (since these both target commits rather than branches). It was also doing un-needed extra work by submitting the PR three times (because of the multi-platform strategy). Sorry I didn't catch this in my prior commit.

[mavrosxristoforos]

Is this ready for review?

[bmos]

Is is now! It's now pretty much like the old action but targets node20.
If the idea of having it auto-build and create a PR when you commit changes that should be its own file with more limited triggering (as in this action at 23c9df2 but without the first job).

[mavrosxristoforos]

So, does it create a PR for auto-building now?

[bmos]

No, although I'm willing to rework this to retain that feature if you'd prefer.

[mavrosxristoforos]

So, for future contributors, would we need to build before committing?
I'm ok with both options. Does it create any PRs now? If yes, what for?

[bmos]

It does not create a PR at all.
It only runs the build process to ensure it completes without errors.

[mavrosxristoforos]

I think it's best this way...