keycloak: update quay.io/keycloak/keycloak Docker tag to v26.3.0

Author: renovate[bot]

keycloak/kustomization.yaml

@@ -22,4 +22,4 @@ generators:
   - secret-generator.yaml
 images:
   - name: quay.io/keycloak/keycloak
-    newTag: 26.1.4@sha256:044a457e04987e1fff756be3d2fa325a4ef420fa356b7034ecc9f1b693c32761
+    newTag: 26.3.0@sha256:08a31919cfcd814bf1b465142b1a716c4d1a8830f772bb5c9dffcbd96de3fba6