Reword description

mmv1/products/certificatemanager/Certificate.yaml

@@ -135,7 +135,7 @@ properties:
       ALL_REGIONS: Certificates with ALL_REGIONS scope are served from all GCP regions (You can only use ALL_REGIONS with global certs).
       See https://cloud.google.com/compute/docs/regions-zones.
 
-      CLIENT_AUTH: Certificates with CLIENT_AUTH scope are used to configure a load balancer's backend service to use mTLS.
+      CLIENT_AUTH: Certificates with CLIENT_AUTH scope are used by a load balancer (TLS client) to be presented to the backend (TLS server) when backend mTLS is configured.
       See https://cloud.google.com/load-balancing/docs/backend-authenticated-tls-backend-mtls#client-certificate.
     immutable: true
     diff_suppress_func: 'certManagerDefaultScopeDiffSuppress'