You have overriden the standard menu, and trying to set the group attributes.. which will just append the groups to it, as it is Many2many field,.. So use (6,0) which will replace the groups

Here your code should go like this....

<record model="ir.ui.menu" id="account.menu_account_config">
            <field name="groups_id" eval="[(6,0, [ref('module1.group_hidden)])]"/>  
        </record>

Refer Docs: ORM Methods