[MIG] partner_statement: Migration to 13.0

[UPD] Update partner_statement.pot

[UPD] README.rst

Update translation files

Updated by "Update PO files to match POT (msgmerge)" hook in Weblate.

Translation: account-financial-reporting-13.0/account-financial-reporting-13.0-partner_statement
Translate-URL: https://translation.odoo-community.org/projects/account-financial-reporting-13-0/account-financial-reporting-13-0-partner_statement/

partner_statement/wizard/statement_common.py

@@ -56,7 +56,6 @@ class StatementCommon(models.AbstractModel):
         else:
             self.date_end = fields.Date.context_today(self)
 
-    @api.multi
     def button_export_pdf(self):
         self.ensure_one()
         return self._export()