* Clarify docs around using either Consul or Vault managed PKI paths
The current docs can be misread to indicate that you need both the
Consul and Vault managed PKI Paths policies. The [Learning Tutorial](https://learn.hashicorp.com/tutorials/consul/vault-pki-consul-connect-ca?in=consul/vault-secure#create-vault-policies)
is clearer. This tries to make the original docs as clear as the
learning tutorial
* Clarify that PKI secret engines are used to store certs
Co-authored-by: Blake Covarrubias <blake.covarrubias@gmail.com>