jenkinsfiles: remove symlink for kubernetes-upstream.Jenkinsfile
jenkinsfiles: remove symlink for kubernetes-upstream.Jenkinsfile

As files are currently stored in the `jenkinsfiles/` we can safely
remove this file.

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

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