ocis_keycloak: Fix deployment example

After commit 52951b42b0 we need to set PROXY_USER_CS3_CLAIM and
PROXY_USER_OIDC_CLAIM for the keycloak example to still work.

Also update release notes to mentions the changed default.

deployments/examples/ocis_keycloak/docker-compose.yml

@@ -69,6 +69,8 @@ services:
       OCIS_LOG_LEVEL: ${OCIS_LOG_LEVEL:-info}
       OCIS_LOG_COLOR: "${OCIS_LOG_COLOR:-false}"
       PROXY_TLS: "false" # do not use SSL between Traefik and oCIS
+      PROXY_USER_OIDC_CLAIM: "preferred_username"
+      PROXY_USER_CS3_CLAIM: "username"
       # INSECURE: needed if oCIS / Traefik is using self generated certificates
       OCIS_INSECURE: "${INSECURE:-false}"
       OCIS_ADMIN_USER_ID: ""