net/keycloak: Update 26.5.7 => 26.6.1
Release Notes:
https://www.keycloak.org/2026/04/keycloak-2660-released
https://www.keycloak.org/2026/04/keycloak-2661-released
PR: 295099
Security: CVE-2026-4366
Security: CVE-2026-4633
Sponsored by: UNIS Labs
MFH: 2026Q2
(cherry picked from commit 89db17ef247e9222623ff64f65487830ba21bebd)