chore: Improve error message for deleting EC2NodeClass

[jonathan-innis]

Fixes #5656

Description

This updates our error that we send back to users when EC2NodeClasses that are in a terminating state that we are treating as NotFound

How was this change tested?

make presubmit
make apply

Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: #
• No

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[coveralls]

Pull Request Test Coverage Report for Build 7891779882

Details

• -12 of 13 (7.69%) changed or added relevant lines in 1 file are covered.
• 3 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.2%) to 82.497%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/cloudprovider/cloudprovider.go	1	13	7.69%

Files with Coverage Reduction	New Missed Lines	%
pkg/providers/amifamily/ami.go	1	90.32%
pkg/cloudprovider/cloudprovider.go	2	72.35%

Totals
Change from base Build 7889953331:	-0.2%
Covered Lines:	5015
Relevant Lines:	6079

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💛 - Coveralls

[engedaam]

LGTM 🚀