databases/ruby-mysql2: update to 0.5.6

0.5.6 (2024-02-08)

* Add an option to set a custom SSL certificates pem files directory in
  test.
* Session tracking: account for MySQL 8 reporting statement_id changes
  along with other system variables (#1324)
* Support utf8mb3 charset naming for MySQL 8 and MariaDB 10.6 (#1323)
* use mysql_options if mysql_ssl_set isn't available for mysql 8.3 support
* fix: mysql 8.3 ssl settings

(taca)