Cannot build CentOS 7 images (and that causes CI failures)

[kkebo]

Recently, CentOS 7 has reached EOL and mirrorlist.centos.org is no longer available according to the following links.

• https://stackoverflow.com/questions/78692851/could-not-retrieve-mirrorlist-http-mirrorlist-centos-org-release-7arch-x86-6
• https://serverfault.com/questions/1161816/mirrorlist-centos-org-no-longer-resolve
• https://blog.centos.org/2023/04/end-dates-are-coming-for-centos-stream-8-and-centos-linux-7/

This is not only a problem for those who want to use CentOS 7, but also causes all swiftlang/swift:nightly-main* images not to be updated.

Error logs:

https://ci.swift.org/view/all/job/publish-nightly-main-docker-images-aarch64/847/execution/node/29/log/

#6 [ 2/12] RUN yum install -y centos-release-scl-rh
#6 0.322 Loaded plugins: fastestmirror, ovl
#6 0.448 Determining fastest mirrors
#6 0.458 Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=container error was
#6 0.458 14: HTTP Error 502 - Bad Gateway

(All: https://ci.swift.org/view/all/job/publish-nightly-main-docker-images-aarch64/)

[kkebo]

It seems that the CI job for CentOS 7 has been deleted.

https://ci.swift.org/view/all/job/publish-nightly-main-docker-images-aarch64/

So this issue is not critical now. Please feel free to close this if it's not planned.