[menubar] Menubar `disabled` prop does not disable menus

# Bug report

## Current behavior

Passing the `disabled` prop to the `Menubar` component does not disable the menus.

## Expected behavior

I expected the menus within the menubar to be disabled when this prop is set.

## Reproducible example

https://codesandbox.io/p/sandbox/disabled-menubar-dkg635

## Base UI version

1.0.0-beta.3