Switch back to upstream GCR images for openstack-cloud-controller-manager and cinder-csi-plugin

[ialidzhikov]

How to categorize this PR?

/area networking
/area open-source
/kind enhancement
/platform openstack

What this PR does / why we need it:
With kubernetes/cloud-provider-openstack#1540 openstack-cloud-controller-manager and cinder-csi-plugin images are pushed to GCR. See https://github.com/kubernetes/k8s.io/blob/main/k8s.gcr.io/images/k8s-staging-provider-os/images.yaml
Hence, we do no longer need to maintain our copies for 1.24, 1.25, 1.26.

Which issue(s) this PR fixes:
See above.

Special notes for your reviewer:
N/A

Release note:

provider-openstack does no longer use Gardener GCR copies for `openstack-cloud-controller-manager` and `cinder-csi-plugin` in versions 1.24, 1.25 and 1.26. Instead, the upstream GCR container images are used (`registry.k8s.io/provider-os/openstack-cloud-controller-manager` and `registry.k8s.io/provider-os/cinder-csi-plugin`).

The following images are updated:
- registry.k8s.io/provider-os/cinder-csi-plugin: v1.24.5 -> v1.24.6 (for Kubernetes 1.24 Shoots)
- registry.k8s.io/provider-os/cinder-csi-plugin: v1.25.3 -> v1.25.5 (for Kubernetes 1.25 Shoots)
- registry.k8s.io/provider-os/cinder-csi-plugin: v1.26.0 -> v1.26.2 (for Kubernetes 1.26 Shoots)

[ialidzhikov]

/assign @timebertt @robinschneider

[timebertt]

/lgtm

[gardener-robot]

@timebertt Command /lgtm is not available to you but only to a Maintainer, Member.

[MartinWeindel]

/lgtm

[ialidzhikov]

I now deleted the images

• eu.gcr.io/gardener-project/3rd/k8scloudprovider/openstack-cloud-controller-manager:{v1.24.6,v1.25.5,v1.26.2}
• eu.gcr.io/gardener-project/3rd/k8scloudprovider/cinder-csi-plugin:{v1.24.5,v1.25.3,v1.26.0}

as these images were added only for few hours to provider-openstack@master and then this PR was merged.