add ENA to initialism list w/ preventions

[bwagner5]

Issue #, if available:
aws-controllers-k8s/ec2-controller#17

Description of changes:

• Add ENA to initialism list and prevent "Enable" -> "ENAble" and "Enabling" -> "ENAbling"

Grep to find other Ena words in aws models:

$ grep -r 'Ena[a-zA-Z]*' -o .  | sort | uniq | grep -v "Enabl"
./ec2/2016-11-15/api-2.json:EnaSupport
./ec2/2016-11-15/docs-2.json:EnaSupport
./ec2/2016-11-15/examples-1.json:EnaSupport

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

[RedbackThomson]

Hopefully no-one is enamoured enough with this prefix to enact a new policy to enable it in any other models.

But don't quote me on that.

/lgtm

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[jaypipes]

Hopefully no-one is enamoured enough with this prefix to enact a new policy to enable it in any other models.

But don't quote me on that.

/lgtm

I see what you did there.