test/upgrade: use the unreleased helm chart of stable branches
test/upgrade: use the unreleased helm chart of stable branches

The upgrade tests are using the official helm charts with unreleased
Cilium images. This can might cause the upgrade tests to fail in case
the changes done in the unreleased Cilium versions require a new helm
chart release. To fix this problem the upgrade tests will now use the
unreleased helm charts as well.

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

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