keycloak: update quay.io/keycloak/keycloak Docker tag to v26.4.0

Author: renovate[bot]

keycloak/kustomization.yaml

@@ -22,4 +22,4 @@ generators:
   - secret-generator.yaml
 images:
   - name: quay.io/keycloak/keycloak
-    newTag: 26.3.2@sha256:98fab020a3a490aba0978f237e2a06cd0ea42bf149c6cf10f11c0aaf27728ff2
+    newTag: 26.4.0@sha256:5f3fb534cde6bf006d79f5912473e5d2c828c707cdfc52e16972803aca9d43dd