msxml3: Fix memory leak.

dlls/msxml3/xmlelem.c

@@ -340,6 +340,8 @@ static HRESULT WINAPI xmlelem_get_text(IXMLElement *iface, BSTR *p)
     content = xmlNodeGetContent(This->node);
     *p = bstr_from_xmlChar(content);
     TRACE("returning %s\n", debugstr_w(*p));
+
+    xmlFree(content);
     return S_OK;
 }