chore(deps): update quay.io/keycloak/keycloak docker tag to v26.4.0 (apache#2719)

Author: renovate-bot

getting-started/keycloak/docker-compose.yml

@@ -79,7 +79,7 @@ services:
         /polaris/create-catalog.sh realm-mixed $$token
 
   keycloak:
-    image: quay.io/keycloak/keycloak:26.3.5
+    image: quay.io/keycloak/keycloak:26.4.0
     ports:
       - "8080:8080"
     environment: