Remove insenstive language like "blacklist", "whitelist", "master", and "slave"

[rberlind]

There are no references to "blacklist".

We'll want to rename https://github.com/hashicorp/vault-guides/blob/master/governance/sentinel/egp-okta-user-whitelist.sentinel to egp-okta-user-allowlist.sentinel and change reference to it in https://github.com/hashicorp/vault-guides/blob/master/governance/sentinel/README.md to remove "whitelist".

We'll want to change variable names in https://github.com/hashicorp/vault-guides/blob/master/secrets/spring-cloud-vault/kubernetes/terraform/variables.tf and their use in https://github.com/hashicorp/vault-guides/blob/master/secrets/spring-cloud-vault/kubernetes/terraform/main.tf to remove "master"

If possible, make changes in https://github.com/hashicorp/vault-guides/blob/master/shared/vault/scripts/vault-k8s-helm.sh to remove "master"

"master" is used in https://github.com/hashicorp/vault-guides/blob/master/identity/vault-agent-k8s-demo/terraform-gcp/main.tf, but this is because that is what the Terraform google_container_cluster resource uses.

remove "master" from https://github.com/hashicorp/vault-guides/blob/master/identity/vault-agent-k8s-demo/terraform-gcp/README.md which refers to "Kubernetes master". It is in a comment, so could be removed.

https://github.com/hashicorp/vault-guides/blob/master/operations/raft-storage/aws/main.tf refers to "master key" but only in a comment, so it could be removed.

https://github.com/hashicorp/vault-guides/blob/master/operations/aws-kms-unseal-ha/terraform/README.md and https://github.com/hashicorp/vault-guides/blob/master/governance/audit/README.md refer to Vault's "master key" in text.