[FIX] doc: fit code example to new API

When using this code as is, the 'ids' variable throws an exception for not
being defined. In the new API, 'ids' is no longer given as a function variable
but as a variable within 'self'.

close #3406

doc/reference/reports.rst

@@ -65,9 +65,9 @@ render_html method.  Classically, this method returns a call to the original
             report_obj = self.env['report']
             report = report_obj._get_report_from_name('<<module.reportname>>')
             docargs = {
-                'doc_ids': ids,
+                'doc_ids': self._ids,
                 'doc_model': report.model,
-                'docs': self.env[report.model].browse(ids),
+                'docs': self,
             }
             return report_obj.render('<<module.reportname>>', docargs)