databases/mysql80-server: Update my.cnf.sample

Update deprecated configs in my.cnf.sample

Some configs in my.cnf.sample are now deprecated. These should be replaced with their replacement, or removed if there is no replacement.

• Replace deprecated slave-load-tmpdir with replica-load-tmpdir
• Remove deprecated master-info-repository (it was set to the default)
• Remove deprecated relay-log-info-repository (it was set to the default)
• Replace deprecated expire_logs_days with binlog_expire_logs_seconds (multiply 30 days by 24 * 60 * 60)
• Replace deprecated innodb_log_file_size with innodb_redo_log_capacity (preserving the same configured capacity, which was set to 256M * 2 log files)
• Remove deprecated skip-symbolic-links (it is the default)

PR: 266511
Sponsored by: Netzkommune GmbH