Prerequisites

• I have searched for duplicate or closed issues
• I have validated any HTML to avoid common problems
• I have read the contributing guidelines

Describe the issue

What does this fix?

When using data-bs-auto-close="outside" with nested submenus,
pressing the arrow keys caused multiple submenus to remain open
at the same time instead of auto-closing the previous one.

Root Cause

In dataApiKeydownHandler, instance.show() was called
unconditionally on every arrow key press, re-showing already
dismissed dropdowns.

Fix

Wrapped instance.show() with a !instance._isShown() check
so it only opens the dropdown if it is not already visible.

Steps to reproduce

1. Click Demo top level menu
2. Click Submenu 3
3. Press Arrow Up multiple times
4. Previously: all submenus stayed open ❌
5. Now: only current submenu shows ✅

Reduced test cases

What operating system(s) are you seeing the problem on?

Windows

What browser(s) are you seeing the problem on?

Firefox, Chrome

What version of Bootstrap are you using?

v5.3.7