[FIX] account_tax_balance: Make test compatible with others

The test assumes you don't have any other move with taxes in your DB,
which can be happen sometimes, so we need to change assert for being
compatible with this situation.

account_tax_balance/tests/test_account_tax_balance.py

@@ -98,8 +98,7 @@ class TestAccountTaxBalance(TransactionCase):
 
         # exercise search has_moves = True
         taxes = self.env['account.tax'].search([('has_moves', '=', True)])
-        self.assertEqual(len(taxes), 1)
-        self.assertEqual(taxes[0].name, u"Tax 10.0%")
+        self.assertIn(tax, taxes)
 
         # testing buttons
         tax_action = tax.view_tax_lines()