Fix absence of skopeo Docker image

On August the 29th, all quay.io/containers/skopeo images have been deleted due to a potential credentials leak, see:

On August 23rd it was discovered that the credentials for several robot service accounts with write-access to the container-images could have leaked. Upon discovery, the credentials were invalidated. The earliest possible leak opportunity was around March 10th, 2022.
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We realize this issue has the potential to impact not only direct, but also indirect use, such as base-images. The safety and integrity of these images has and must take priority. At this time, all images have been disabled. We will restore originals and/or rebuild fresh copies based on further safety analysis.

This is causing build failure in the Platform CI, especially all jobs that uses a CentOS 7 based builder, see:

skopeo copy docker://docker.platform.dev.nuxeo.com/nuxeo/nuxeo-base:2021.43.4 docker://docker.platform.dev.nuxeo.com/nuxeo/nuxeo-base:2021.x
[2023-08-29T14:47:20.822Z] Unable to find image 'quay.io/containers/skopeo:v1.9.2' locally
[2023-08-29T14:47:21.390Z] docker: Error response from daemon: unknown: Tag v1.9.2 was deleted or has expired. To pull, revive via time machine.

A potential mid-term solution would be to use an user image such as https://hub.docker.com/r/bdwyertech/skopeo