Alpine 386 builds failing for v12 and v14

[nschonni]

Looks like it's failing consistently https://doi-janky.infosiftr.net/job/multiarch/view/images/view/node/
I believe official support was dropped in v10, but it looks like it is currently passing anyway.
Should we remove the 386 architecture entirely or just for v12 and v14

[ttshivers]

Relevant i386 issue for node: nodejs/node#33019
Looks like i386 builds might start working again in node 15 (still experimentally), as reported by someone having success building it in that issue.

It doesn't look like v12 or v14 will have that issue breaking i386 fixed so removing support for just those versions in the official release pipeline might be reasonable for keeping errors or failures meaningful.

I think it might be useful to keep i386 builds for v10 as long as it's still supported.