databases/xtrabackup80: Mark DEPRECATED

• This version has reached EOL and should be marked DEPRECATED in favor of databases/xtrabackup84.
• Set EXPIRATION_DATE 2026-09-30

PR: 296505
Approved by: eugene@zhegan.in (maintainer-timeout)

(cherry picked from commit 10100f895d37fe09aa28b80575f5ad40817553a1)