gen_stub: Update PHP-Parser to 5.6.0 (#19271)

Includes support for declaring functions named `clone`, so update the stub file
where `clone` is declared to remove the `_clone` workaround.

Author: DanielEScherzer

Zend/zend_builtin_functions.stub.php

@@ -8,7 +8,7 @@ class stdClass
 }
 
 /** @refcount 1 */
-function _clone(object $object, array $withProperties = []): object {}
+function clone(object $object, array $withProperties = []): object {}
 
 function exit(string|int $status = 0): never {}
 

Zend/zend_builtin_functions_arginfo.h

@@ -959,9 +959,6 @@ class FunctionName implements FunctionOrMethodName {
     private /* readonly */ Name $name;
 
     public function __construct(Name $name) {
-        if ($name->name === '_clone') {
-            $name = new Name('clone', $name->getAttributes());
-        }
         $this->name = $name;
     }
 
@@ -6059,7 +6056,7 @@ function initPhpParser() {
     }
 
     $isInitialized = true;
-    $version = "5.5.0";
+    $version = "5.6.0";
     $phpParserDir = __DIR__ . "/PHP-Parser-$version";
     if (!is_dir($phpParserDir)) {
         installPhpParser($version, $phpParserDir);