fix(helm): fix syntax in loki-egress-dns CiliumNetworkPolicy manifest

[kkoppel]

What this PR does / why we need it:
Enables deploying CiliumNetworkPolicy via the Loki Helm chart with Terraform + Helm provider v3.1.0+ by fixing syntax of the loki-egress-dns manifest

Which issue(s) this PR fixes:
Fixes #20218

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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