Upgrades are not grouped in a single PR when auditlog-forwarder is released

[dimityrmirchev]

What happened:
When a new version of auditlog-forwarder was release the following PR was opened #76 which did not upgrade the dependency in go.mod. This leads to the fact that we use new version of the image, but the dependency to the API stays outdated. In g/g we use renovate to handle this case https://github.com/gardener/gardener/blob/master/.github/renovate.json5 see gardener/gardener#13615. We might consider a similar approach.