FIX missing date in invoice

The second invoice created has no explicit so taking the current date could lead to failing tests because the invoice is out of search as the the setup sets date_from as time.strftime("%Y-%m-01") and date_to as time.strftime("%Y-%m-28"). So i choose the easy way by setting an explicit date for the invoice.

account_financial_report/tests/test_vat_report.py

@@ -166,6 +166,7 @@ class TestVATReport(common.TransactionCase):
             self.env["account.move"].with_context(default_type="out_invoice")
         )
         move_form.partner_id = self.env.ref("base.res_partner_2")
+        move_form.invoice_date = time.strftime("%Y-%m-04")
         with move_form.invoice_line_ids.new() as line_form:
             line_form.product_id = self.env.ref("product.product_product_4")
             line_form.quantity = 1.0