[skip-revcheck] Fix Dom\HtmlDocument::saveXml() typo (#4391)

Author: Fan2Shrek

reference/dom/dom/htmldocument/savexml.xml

@@ -13,7 +13,7 @@
    <methodparam choice="opt"><type>int</type><parameter>options</parameter><initializer>0</initializer></methodparam>
   </methodsynopsis>
   <simpara>
-   Serializes the document as an <acronym>XML</acronym> stirng.
+   Serializes the document as an <acronym>XML</acronym> string.
   </simpara>
  </refsect1>