fix: remove Flux validation and fix YAML linting

- Remove Flux validation job (repo doesn't contain Flux resources)
- Fix trailing spaces in best-practices workflow
- Add missing newline at end of znc/statefulset.yaml

Flux validates Kustomization CRDs, not plain manifests. Since this
repo only contains the manifests deployed by Flux (not the Flux
resources themselves), the validation doesn't apply.

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Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

znc/statefulset.yaml

@@ -87,4 +87,4 @@ spec:
           - ReadWriteOnce
         resources:
           requests:
-            storage: 4Gi
+            storage: 4Gi