Fix signature of xml.dom.minidom.Document.toprettyxml(). (GH-10814)

Doc/library/xml.dom.minidom.rst

@@ -163,7 +163,7 @@ module documentation.  This section lists the differences between the API and
       The :meth:`toxml` method now preserves the attribute order specified
       by the user.
 
-.. method:: Node.toprettyxml(indent="", newl="", encoding="")
+.. method:: Node.toprettyxml(indent="\t", newl="\n", encoding=None)
 
    Return a pretty-printed version of the document. *indent* specifies the
    indentation string and defaults to a tabulator; *newl* specifies the string