Replace `cloudfoundry/cf-k8s-networking` Helm charts in `vendir` manager docs

[HonkingGoose]

Describe the proposed change(s).

The vendir manager docs need new Helm Chart examples, because the cloudfoundry/cf-k8s-networking repository is archived.

I do not know enough about Helm Charts or vendir to find a good replacement for us.

If you know about Helm Charts or vendir, please respond to this issue, so we can assign you to work on the docs. :wink:

Links to the affected parts:

• Renovate docs, vendir manager
• Source file: lib/modules/manager/vendir/readme.md

[HonkingGoose]

I wanted to apply the manager:vendir label to this issue, but we do not have that label yet.

If you care about this as a maintainer, please create the label, and apply it to the issue. :wink: