[FIX] l10n_be_intrastat: typo EXTRF now 29/19

Intrastat was modified on january 2019 to backport some features for new
regulation of belgian intrastat in c5a8e3975.

There was a coding typo so EXTRF was <Report/> code attribute instead.

sources:
 https://www.nbb.be/doc/dq/e_pdf_ex/docxml-en.pdf
 https://www.nbb.be/doc/dq/f_pdf_ex/docxml-fr2019.pdf

opw-1948336
closes #31875

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>

addons/l10n_be_intrastat/wizard/xml_decl.py

@@ -222,11 +222,13 @@ class XmlDeclaration(models.TransientModel):
         if dispatchmode:
             mode1 = 'out_invoice'
             mode2 = 'in_refund'
+            extrf = "29"
             declcode = self._get_expedition_code(extendedmode)
             declform = self._get_expedition_form(extendedmode)
         else:
             mode1 = 'in_invoice'
             mode2 = 'out_refund'
+            extrf = "19"
             declcode = self._get_reception_code(extendedmode)
             declform = self._get_reception_form(extendedmode)
 
@@ -271,7 +273,7 @@ class XmlDeclaration(models.TransientModel):
         invoicelines = self.env['account.invoice.line'].browse(invoicelines_ids)
 
         for inv_line in invoicelines:
-            linekey = self._get_intrastat_linekey(declcode, inv_line, dispatchmode, extendedmode)
+            linekey = self._get_intrastat_linekey(extrf, inv_line, dispatchmode, extendedmode)
             if linekey is None:
                 continue