Update etcd-certificates.adoc

The etcd-metric-client client secret is present in openshift-etcd namespace, and not in openshift-config / openshift-monitoring / openshift-kube-apiserver namespaces starting from RHOCP version 4.16 and above.

Previously till RHOCP version 4.15, it was present in the openshift-config namespace.

Author: K-h-u-s-h-i-M

security/certificate_types_descriptions/etcd-certificates.adoc

@@ -27,7 +27,7 @@ These certificates are only managed by the system and are automatically rotated.
 etcd certificates are used for encrypted communication between etcd member peers and encrypted client traffic. The following certificates are generated and used by etcd and other processes that communicate with etcd:
 
 * Peer certificates: Used for communication between etcd members.
-* Client certificates: Used for encrypted server-client communication. Client certificates are currently used by the API server only, and no other service should connect to etcd directly except for the proxy. Client secrets (`etcd-client`, `etcd-metric-client`, `etcd-metric-signer`, and `etcd-signer`) are added to the `openshift-config`, `openshift-monitoring`, and `openshift-kube-apiserver` namespaces.
+* Client certificates: Used for encrypted server-client communication. Client certificates are currently used by the API server only, and no other service should connect to etcd directly except for the proxy. Client secrets (`etcd-client`, `etcd-metric-client`, `etcd-metric-signer`, and `etcd-signer`) are added to the `openshift-config`, `openshift-etcd`, `openshift-monitoring`, and `openshift-kube-apiserver` namespaces.
 * Server certificates: Used by the etcd server for authenticating client requests.
 * Metric certificates: All metric consumers connect to proxy with metric-client certificates.