[EuiSelectable] Remove duplicated `state` instructions for a11y

[tkajtoch]

Requestor

@jorgeoliveira117

Problem Statement

Currently, the AT output is too verbose. We provide custom text instructions as well as aria-checked and aria-activedescendant attributes, which result in duplicated information.

Proposed Solution

We should remove the custom state instructions.

Use Case

This is a general improvement to assistive technology user experience.

elastic/kibana#219222

Value / Impact

This will fix duplicated information in assistive technology software.

Urgency

This was reported internally and raised by @L1nBra. Since this issue is about duplicated information and not a lack of information, it could be treated with slightly less urgency. However, the fix is simple, and I feel we should get to it straight away to protect our backlog.

Do alternatives or workarounds exist?

Not really

Related code or customizations

https://github.com/elastic/eui/blob/main/packages/eui/src/components/selectable/selectable_list/selectable_list_item.tsx#L322

Additional context (Optional)

elastic/kibana#219222

[JasonStoltz]

Thank you for adding this issue. We've triaged it to determine priority and next steps:

• New status: Backlog
• Priority: We are not prioritizing this work.
• Next steps: We are unlikely to complete this work, but we’d happily review a pull request if you’d like to contribute a PR.

If you believe this should be prioritized differently, please feel free to add more context here (e.g., how it impacts your work, or how broadly it might affect other users). That helps us re-evaluate priorities.

Notes from Triage:
We're tracking and prioritizing this in the context of a larger set of accessibility related issues. As this is related to a Level 3 defect, it's low on our priority list.