fix(pmm): remove namespace from ClusterRole metadata

[franco-viotti]

Summary

• remove pmm.includeNamespace from charts/pmm/templates/clusterrole.yaml so rendered ClusterRole does not include metadata.namespace
• bump charts/pmm/Chart.yaml version from 1.6.0 to 1.6.1

Why

ClusterRole is cluster-scoped and should not carry a namespace. Including metadata.namespace can cause persistent GitOps drift.

Scope

This PR intentionally focuses on the namespace defect and chart version bump only.

Related: #834

[it-percona-cla]

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1 out of 2 committers have signed the CLA.

✅ JiriCtvrtka
❌ franco-viotti
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[JiriCtvrtka]

@franco-viotti could you sign CLA license? Thank you.