fix the node clean up failure without auto mode

[wwvela]

Issue #, if available:
Find below error when deleting unmanaged node group without AutoMode. Fix by only clean up these resources when it is AutoMode

January 06, 2025 at 15:02 (UTC-8:00)
Error: failed to delete node pool: no matches for kind "NodePool" in version "karpenter.sh/v1"
	
January 06, 2025 at 15:02 (UTC-8:00)
I0106 23:02:28.920402 12 node.go:289] placeholder deployment does not exist: kubetest2-eksapi-f0b52762-d024-466e-b8dd-08ba7cf96d3e
	
January 06, 2025 at 15:02 (UTC-8:00)
I0106 23:02:28.920421 12 node.go:218] deleting node pool...
	
January 06, 2025 at 15:02 (UTC-8:00)
I0106 23:02:28.205830 12 node.go:586] nodegroup does not exist: kubetest2-eksapi-f0b52762-d024-466e-b8dd-08ba7cf96d3e
	
January 06, 2025 at 15:02 (UTC-8:00)
I0106 23:02:28.205850 12 node.go:286] deleting placeholder deployment...