contributing/release: remove update NEWS.rst step
contributing/release: remove update NEWS.rst step

`git shortlog v1.0.2..` can be executed by anyone in their terminal and
since we now have auto-generated release-notes it does not make sense to
run this step anymore.

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

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