[docs] missing warning for offcanvas dark classes

Created by: bastienmoulia

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

In the offcanvas doc, there is some dark classes without the warning to use data-bs-theme="dark".

Also in close button, the Heads up! is an info and not a warning.

Reduced test cases

https://getbootstrap.com/docs/5.3/components/offcanvas/#dark-offcanvas

https://getbootstrap.com/docs/5.3/components/close-button/#dark-variant

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

Windows

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

Chrome

What version of Bootstrap are you using?

5.3.0