net/keycloak: Update 26.6.1 => 26.6.2 (fix 18 CVEs)

Release Notes:
https://www.keycloak.org/2026/05/keycloak-2662-released

PR: 295416
Security: CVE-2026-33871
Security: CVE-2026-33870
Security: CVE-2026-4628
Security: CVE-2026-37980
Security: CVE-2026-5588
Security: CVE-2026-6856
Security: CVE‐2026‐0636
Security: CVE‐2026‐3505
Security: CVE‐2026‐5598
Security: CVE-2026-7307
Security: CVE-2026-7504
Security: CVE-2026-7571
Security: CVE-2026-7507
Security: CVE-2026-37982
Security: CVE-2026-37979
Security: CVE-2026-37978
Security: CVE-2026-4630
Security: CVE-2026-37981
Sponsored by: UNIS Labs
MFH: 2026Q2