fix: remove redundant namespace of cluster-scoped resource

[djmcgreal-cc]

which causes problems if you're validating the YAML e.g. when using kubernetes_manifest terraform resource.

Sorry, this is a tiny change, I haven't the time to read the below in the hope it ain't relevant...

Description:

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[djmcgreal-cc]

@aws-maens , @micwade-aws , @rgrandhiamzn ? tiny change here!