chore(Mixin): Fix per_namespace_label not used

[Syndlex]

Mixin not using per_namespace_label in generation of Dashboards.

Mixin is not changing when per_namespace_label is set.

What this PR does / why we need it:

Which issue(s) this PR fixes:

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
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