Add allowedNamespaces spec to helm chart values.yaml

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Recently allowedNamespaces was added to the vaultauth crd to allow multiple namespaces use the cr. When installing VSO via helm and setting defaultAuthMethod.enabled=true, there is no field for allowedNamespaces so after the cr is created, a manual edit is required.

This presents a challenge when using a gitops tool like argocd to manage the cr as it wants to overwrite the manual change

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add a field for allowedNamespaces in the vaules.yaml file that will apply to the vaultauth cr when created via helm

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**Additional context**
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Start in the Helm chart's values.yaml and trace how defaultAuthMethod.enabled values are applied when the VaultAuth custom resource is created. Add the allowedNamespaces value to that configuration path, then verify that a Helm installation produces the field in the VaultAuth resource.

Written by the indexing model from the issue text.