Spreadsheet: Make the 'Help' window accessory

Userland/Applications/Spreadsheet/HelpWindow.cpp

@@ -64,6 +64,7 @@ HelpWindow::HelpWindow(GUI::Window* parent)
     resize(530, 365);
     set_title("Spreadsheet Functions Help");
     set_icon(Gfx::Bitmap::try_load_from_file("/res/icons/16x16/app-help.png"));
+    set_accessory(true);
 
     auto& widget = set_main_widget<GUI::Widget>();
     widget.set_layout<GUI::VerticalBoxLayout>();