The accounting test suite was tidied by removing duplicate helper code and old commented-out test sections. This is an internal maintenance change that makes future accounting quality checks easier to manage without changing customer-facing behavior.

This commit cleans up the test suite within the `account_accountant` module by removing redundant methods and old commented code.

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Forward-Port-Of: odoo/enterprise#130857
Forward-Port-Of: odoo/enterprise#130644