Exclude one clone php-src test

clone($x, ) will parse as a function call, but be printed as
clone($x), which parses as a clone expression. The difference is
harmless.

Author: nikic

test_old/run.php

@@ -121,6 +121,8 @@ function showHelp($error) {
 | Zend.tests.type_declarations.intersection_types.parsing_comment
 # comments in property fetch syntax, not emulated on old PHP versions
 | Zend.tests.gh14961
+# harmless pretty print difference for clone($x, )
+| Zend.tests.clone.ast
 )\.phpt$~x', $file)) {
                 return null;
             }