add scruffy to garbage collect CI images from quay.io
add scruffy to garbage collect CI images from quay.io

To avoid having too many docker image tags caused by the builds of PRs,
we should clean those tags every week.

Signed-off-by: André Martins <bc9800b9d52a24cce72a73dd528afed53f10e5fc@cilium.io>

michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,tklauser/cilium