security/aws-iam-authenticator: Update to 0.7.18

Changelogs:
https://github.com/kubernetes-sigs/aws-iam-authenticator/releases/tag/v0.7.16
https://github.com/kubernetes-sigs/aws-iam-authenticator/releases/tag/v0.7.17
https://github.com/kubernetes-sigs/aws-iam-authenticator/releases/tag/v0.7.18