chore(deps): update quay.io/keycloak/keycloak docker tag to v26.3

Author: renovate[bot]

docker-compose.yml

@@ -921,7 +921,7 @@ services:
       NEXTCLOUD_URL: http://nextcloud
 
   keycloak:
-    image: quay.io/keycloak/keycloak:26.1
+    image: quay.io/keycloak/keycloak:26.3
     expose:
       - 8080
     volumes: