[MIG] account_financial_report: Migration to 14.0

Since v14, Odoo defines the `__slots__` attribute in the `BaseModel` class (ea3e39506a)
This makes it impossible to add attributes to an instance like it was done here in v13.
The use of the `report_data` dictionary passed between method is the closes and simples solution to this "issue".

TT26415

Co-authored-by: Alex Cuellar <acuellar@grupoyacck.com>

account_financial_report/tests/test_general_ledger.py

@@ -86,7 +86,7 @@ class TestGeneralLedgerReport(common.TransactionCase):
             ],
         }
         move = self.env["account.move"].create(move_vals)
-        move.post()
+        move.action_post()
 
     def _get_report_lines(self, with_partners=False):
         centralize = True