Publish linux/amd64 docker images for snapshot builds only

[smashedr]

I did some research and it seems the correct way to publish a multi-architecture build under a single tag is to do it simultaneously.

0 shane@jammy [/home/shane]$ docker pull shieldsio/shields:next
next: Pulling from shieldsio/shields
no matching manifest for linux/amd64 in the manifest list entries

That will make the entire build take the full duration of ~35 minutes. At a glance I don't see master being merged to more frequently than 35 minutes apart, so I have also included the next build here, but that can easily be removed.

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[chris48s]

Merging lots of PRs close together is something we do frequently e.g:

Even if we didn't, having to wait ~35 minutes from merging something to having an image ready to deploy every time is just going to be too annoying. I think if the only way to do this is to push both together, we go with what I suggested in #10441 (comment) - arm64 on snapshot tags only.

[smashedr]

Ok, I can remove the arm64 from next, and just leave it on the release branch build.

[chris48s]

Cool. I am planning to do the next snapshot release later today so we'll test the process and (hopefully) have a working dual arch image available this time.

[chris48s]

[smashedr]

Looks good ✅
I was able to run shieldsio/shields:server-2024-09-02 on my development server and deploy it to my arm64 swarm server.