Unpublished images of recent OpenWrt versions for x86_64 (and other architectures)

[russoz]

As described and (hopefully) fixed in #206 , the building of some architectures started to fail because of upstream changes.

This is affecting other projects, like the Ansible community.openwrt collection (see ansible-collections/community.openwrt#246 and ansible-collections/community.openwrt#251).

See ansible-collections/community.openwrt#246 (comment) for more details.

I also noticed that a recent run of the RootFS workflow failed for the x86_64 architecture:
https://github.com/openwrt/docker/actions/runs/31335680296/job/93305092191