Fix: add label user-grafana pvc for velero

[robinAwallace]

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What kind of PR is this?

Required: Mark one of the following that is applicable:

• kind/feature
• kind/improvement
• kind/deprecation
• kind/documentation
• kind/clean-up
• kind/bug
• kind/other

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Important

Breaking changes should be marked kind/admin-change or kind/dev-change depending on type
Critical security fixes should be marked with kind/security

• kind/admin-change
• kind/dev-change
• kind/security
• kind/adr

What does this PR do / why do we need this PR?

This ensures that the user-grafana pvc is backed up when using velero snapshot feature and the user-grafana pod is down.

Information to reviewers

Checklist

• Proper commit message prefix on all commits
• Change checks:
  • The change is transparent
  • The change is disruptive
  • The change requires no migration steps
  • The change requires migration steps
  • The change upgrades CRDs
  • The change updates the config and the schema
• Documentation checks:
  • The public documentation required no updates
  • The public documentation required an update - [link to change](set-me)
• Metrics checks:
  • The metrics are still exposed and present in Grafana after the change
  • The metrics names didn't change (Grafana dashboards and Prometheus alerts are not affected)
  • The metrics names did change (Grafana dashboards and Prometheus alerts were fixed)
• Logs checks:
  • The logs do not show any errors after the change
• Pod Security Policy checks:
  • Any changed pod is covered by Pod Security Admission
  • Any changed pod is covered by Gatekeeper Pod Security Policies
  • The change does not cause any pods to be blocked by Pod Security Admission or Policies
• Network Policy checks:
  • Any changed pod is covered by Network Policies
  • The change does not cause any dropped packets in the NetworkPolicy Dashboard
• Audit checks:
  • The change does not cause any unnecessary Kubernetes audit events
  • The change requires changes to Kubernetes audit policy
• Falco checks:
  • The change does not cause any alerts to be generated by Falco
• Bug checks:
  • The bug fix is covered by regression tests