Delete obsolete AWS files

[jdmooney]

awf-cf.adoc replaced how-to-set-up-a-cloud-formation-system.adoc/how-to-maintain-a-cloud-formation-system.adoc
aws-multitier.adoc replaced by how-to-set-up-a-multi-tier-system.adoc/how-to-maintain-a-multi-tier-system.adoc
aws-singletier.adoc replaced by how-to-set-up-a-single-tier-system.adoc/how-to-maintain-a-single-tier-system.adoc
aws-single-ami.adoc obsolete. No need to replace.

[reshmabidikar]

Looks good, just one minor comment: Doesn't aws-tools.adoc need to be deleted as done in the earlier PR?

[vnandwana]

The aws-cf.doc has info about updating stack, this is missing in the replaced doc. Could you please take a look? Thank you.

[jdmooney]

@vnandwana could you be more specific? I don't think I am finding the content you are referring to.

[vnandwana]

@jdmooney, sure, aws-cf.adoc has information about updating a CloudFormation stack (see https://github.com/killbill/killbill-docs/blob/v3/userguide/tutorials/aws-cf.adoc#update-configuration).

This information is missing in the docs that has replaced the aws-cf.adoc. We need to add a section in the how-to-set-up-a-cloud-formation-system.adoc/how-to-maintain-a-cloud-formation-system.adoc about updating the configuration.