update documentation link

gui/qt/main_window.py

@@ -371,7 +371,7 @@ class ElectrumWindow(QMainWindow):
         help_menu.addAction(_("&About"), self.show_about)
         help_menu.addAction(_("&Official website"), lambda: webbrowser.open("http://electrum.org"))
         help_menu.addSeparator()
-        help_menu.addAction(_("&Documentation"), lambda: webbrowser.open("http://electrum.org/documentation.html")).setShortcut(QKeySequence.HelpContents)
+        help_menu.addAction(_("&Documentation"), lambda: webbrowser.open("http://electrum.orain.org/")).setShortcut(QKeySequence.HelpContents)
         help_menu.addAction(_("&Report Bug"), self.show_report_bug)
 
         self.setMenuBar(menubar)