[12.0][FIX] excel_import_export: external ids naming.

Because of the naming given to the external ID's, Odoo
interprets all this data as regular module data and when
you update the module and those external ID's are not present
in the module files, it tries to delete them.

excel_import_export/models/xlsx_import.py

@@ -46,7 +46,7 @@ class XLSXImport(models.AbstractModel):
         xml_id = record.get_external_id()
         if not xml_id or (record.id in xml_id and xml_id[record.id] == ''):
             ModelData.create({'name': '%s_%s' % (record._table, record.id),
-                              'module': 'excel_import_export',
+                              'module': '__excel_import_export__',
                               'model': record._name,
                               'res_id': record.id, })
             xml_id = record.get_external_id()