fixed typo, caught on PHP 8.2.0!

PHP Deprecated:  Creation of dynamic property DOMDocument::$preserveWhitespace is deprecated in /home/mumumu/phpdoc/doc-base/configure.php on line 628

Author: mumumu

configure.php

@@ -625,11 +625,11 @@ function generate_sources_file() // {{{
 
 if ($ac['VERSION_FILES'] === 'yes') {
     $dom = new DOMDocument;
-    $dom->preserveWhitespace = false;
+    $dom->preserveWhiteSpace = false;
     $dom->formatOutput       = true;
 
     $tmp = new DOMDocument;
-    $tmp->preserveWhitespace = false;
+    $tmp->preserveWhiteSpace = false;
 
     $versions = $dom->appendChild($dom->createElement("versions"));