fix 8.3 failures

Author: alexandre-daubois

internal/extgen/templates/stub.php.tpl

@@ -9,7 +9,10 @@
 // You may edit the file and remove this comment if you plan to manually maintain
 // this file going forward.
 
-/** @generate-class-entries */
+/**
+ * @generate-class-entries
+ * @generate-legacy-arginfo 80300
+ */
 {{if .Namespace}}
 namespace {{.Namespace}};
 {{end}}