odoo [FW][FIX] account: fix error when opening duplicated Profit and Loss reports

Issue Duplicated Profit and Loss reports fail to open and raise an "invalid operation" error when accessed.

Steps to Reproduce

Install the Accounting module and French localization.
Go to Accounting > Configuration > Accounting > Accounting Reports.
Duplicate the "Profit and Loss (2024)" report.
Navigate to Accounting > Reporting > Profit and Loss.
Attempt to open the duplicated report.
An error occurs.

Root Cause During duplication, the label field of expressions is altered to include a " (copy)" suffix. Some formula expressions rely on exact label matches (e.g., i_1_2024.balance), so when "balance" becomes "balance (copy)", the lookup fails. This mismatch causes a KeyError when resolving subformulas like line_code.balance, breaking the report evaluation.

Fix Prevent the duplication process from altering the label of expressions. There is no functional need to add " (copy)" to these internal labels, as they are not user-facing and must remain stable for formula resolution to work.