#### Issue:
This commit adds a missing account.return.type data in the Oman localization. This is related to the new Accounting Returns #81569

The l10n_om module did not include an account.return.type record, which prevents the "Returns" button (linked to the action_open_returns) from appearing in the Tax Report. As a result, users in Oman are unable to access the Tax Closing form.

Also the l10n_om is a community module, because of that, we need to add a new enterprise module to add the related data for the tax returns.

The visibility of the button is controlled by the following condition: [Code](https://github.com/odoo/enterprise/blob/f924f120cbd04002e21c78b081e1c8006b56a4b6/account_reports/models/account_report.py#L1776)

#### Affected Versions:
18.3 and later

#### Steps to reproduce:

1.Install the l10n_om module
2.Switch to the Oman company
3.Go to Accounting > Reporting > Tax Report
4.The "Returns" button is not visible

#### Expected behavior
The "Returns" button should be visible, allowing the user to generate the closing tax form.

#### Current behavior
The button is hidden due to missing account.return.type data in the Oman localization.

OPW-4943024

Forward-Port-Of: odoo/enterprise#90814