[FIX] base: allow languages with iso code of size 6

Some languages like kabyle ou filipino have the iso code kab_DZ and fil_PH
It was not possible to import it.

closes odoo/odoo#31332

odoo/addons/base/wizard/base_import_language.py

@@ -17,7 +17,7 @@ class BaseLanguageImport(models.TransientModel):
     _description = "Language Import"
 
     name = fields.Char('Language Name', required=True)
-    code = fields.Char('ISO Code', size=5, required=True,
+    code = fields.Char('ISO Code', size=6, required=True,
                        help="ISO Language and Country code, e.g. en_US")
     data = fields.Binary('File', required=True)
     filename = fields.Char('File Name', required=True)