Add workaround for dependency license scan.

[runewake2]

This is a workaround for #1604 that adds an explicit exception for github.com/posener/complete.

To recreate the error this is addressing:

go mod vendor
go list -m -json all | grep posener

Because the source of v1 of posener is not in the vendor directory but posener/v2 exists the check will ignore existing safeguards meant to catch this case. The LICENSE does not exist because the dependency doesn't exist.

Looking for Feedback: I was not able to find a more elegant way of solving this. If you know of one we will probably want to use that instead.

This is intended as a short term solution to unblock Kpt releases by specifically excluding the github.com/posener/complete project from the check.

[seans3]

/lgtm