docs(list-group): Remove disabled for readonly example and fix SR for disabled link

[MarkoOleksiyenko]

Description

Moving the Disabled section into Links and Buttons and fixing the SR for disabled link example

Motivation & Context

List-group non-interactive examples should not be disabled and are ignored by the assistive technology.

I propose to move the Disabled section into the Links and buttons with a precision on how to disable it.

In addition to that the Disabled Link example has to include the href="#" for the SR to properly announce that it is unavailable.

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

• https://deploy-preview-{your_pr_number}--twbs-bootstrap.netlify.app/

Related issues

#40752

[MarkoOleksiyenko]

Hello @julien-deramond , I am working on the accessibility in my project and noticed that with list-group there is an issue with SR while reading the disabled link + the disabled on readonly doesn't make sense (saw that it is mentioned in the #40752).

I wonder what do you think about a small rearrangement with disabled state ?

We can also add the note that with disabled attribute you can omit the aria-disabled="true" for elements like buttons.