[Grafana] Cluster dashboard not displaying clusters on top selector when Retina Standard is deployed

**Describe the bug**
Cluster dashboard not displaying clusters on top selector when Retina Standard is deployed. See sreenshot.


**To Reproduce**
Steps to reproduce the behavior:

1. Deploy Retina with Standard control plane as described in https://retina.sh/docs/Installation/Setup
2. Deploy Prometheus/Grafana as (using the standard control plane file) as described in https://retina.sh/docs/Installation/prometheus
3. Port forward Grafana service as described in https://retina.sh/docs/Installation/grafana
4. Onboard Cluster dashboard
5. Open dashboard - See data flowing, but no cluster can be selected.

**Expected behavior**
Cluster should come up like seen when Retina is deployed with Hubble. See screenshot.


**Platform (please complete the following information):**

- OS: AzureLinux
- Kubernetes Version: 1.28
- Host: AKS
- Retina Version: v0.0.26

**Additional context**
- The feature works correctly when Retina and Prometheus/Grafana are deployed with Hubble control plane.
- I could be relevant to have a test of a Grafana dashboard for multiple instances of Retina.