Update pytest keycloak from 25.0.2 to 26.3

Author: javorszky

tests/data/common/app/keycloak/app.yaml

@@ -30,7 +30,7 @@ spec:
     spec:
       containers:
       - name: keycloak
-        image: quay.io/keycloak/keycloak:25.0.2
+        image: quay.io/keycloak/keycloak:26.3
         args: ["start-dev"]
         env:
         - name: KEYCLOAK_ADMIN