Fix: Correct label indentation in PMM clusterrole.yaml

[ericsanjaya]

Using a 2-space indentation for labels in clusterrole.yaml results in malformed YAML output, as shown below:

# Source: pmm/templates/clusterrole.yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: pmm
  namespace: default
  labels:
  helm.sh/chart: pmm-1.6.0
  app.kubernetes.io/name: pmm
  app.kubernetes.io/instance: pmm
  app.kubernetes.io/component: pmm-server
  app.kubernetes.io/part-of: percona-platform
  app.kubernetes.io/version: "3.7.0"
  app.kubernetes.io/managed-by: Helm

This incorrect nesting causes the Helm validation process to fail. This PR reverts the indentation for the labels section back to 4 spaces to ensure the manifest is valid.

Related Issue
#762

[it-percona-cla]

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