It causes flaky failures like this:

```
+ /usr/bin/docker build --rm -t ruby-fedora-annocheck-copy --build-arg=FILES=ruby -f ../src/tool/annocheck/Dockerfile-copy .
DEPRECATED: The legacy builder is deprecated and will be removed in a future release.
            Install the buildx component to build images with BuildKit:
            https://docs.docker.com/go/buildx/

Sending build context to Docker daemon  556.5MB

Step 1/6 : FROM docker.io/fedora:latest
toomanyrequests: You have reached your pull rate limit. You may increase the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit
```

It seems not that important to maintain the job for backports, so let's
allow failing it until we fix it in master branch.