[12.0][FIX] excel_import_export

Fix Import Excel wizard, cannot download template as in v12
core Odoo prevent download default binary.

excel_import_export_demo/tests/test_xlsx_import_export.py

@@ -41,6 +41,9 @@ class TestXLSXImportExport(TestExcelImportExport):
         with Form(self.env['import.xlsx.wizard'].with_context(ctx)) as f:
             f.import_file = self.export_file
         import_wizard = f.save()
+        # Test sample template
+        import_wizard.get_import_sample()
+        self.assertTrue(import_wizard.datas)
         # Test whether it loads correct template
         self.assertEqual(import_wizard.template_id,
                          self.env.ref('excel_import_export_demo.'