backporting: Update instructions for backporting workflow
backporting: Update instructions for backporting workflow

Commit 02320e added support for working with Cilium forks. Document the
additional steps that are required with this new workflow.

Additionally, workflow scope might be needed with the GitHub token in
some cases that update the corresponding yamls -

``(refusing to allow a Personal Access Token to create or update workflow `.github/workflows/go-check.yaml` without `workflow` scope``

Signed-off-by: Aditi Ghag <436242e0c0af36e461a395c937165372864a99f9@cilium.io>

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