fix: theme switch button issue

[proke03]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

Test Plan

When the enter key was pressed with the theme change button selected, screen reader reads it five times.
There were two reasons for this problem.
First, the button tag had both title and aria-label.
Because the aria live region responds to either text content or aria-label changes, it will respond twice more if both are present.
https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Attributes/aria-relevant
Second, aria-live="polite".

Before fixed
https://user-images.githubusercontent.com/19148682/213901656-ad523fc9-8352-4569-b282-2e31593b348e.mp4

Move title to outter div
https://user-images.githubusercontent.com/19148682/213901679-511f025d-c36e-438f-84f3-71459a93b48f.mp4

Remove aria-live="polite"
https://user-images.githubusercontent.com/19148682/213901697-171e8db5-1167-4cbc-9b66-bb0cda08b6af.mp4

Test links

https://deploy-preview-8569--docusaurus-2.netlify.app/

Deploy preview: https://deploy-preview-_____--docusaurus-2.netlify.app/

Related issues/PRs

#7667

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 77	🟢 97	🟢 100	🟢 100	🟢 90	Report
/docs/installation	🟠 82	🟢 100	🟢 100	🟢 100	🟢 90	Report

[slorber]

Thanks

Is it a bad practice to have both title + aria-label? There are multiple places afaik we do that and not sure why tts would read this label twice 🤔 Any ref material to back this up?

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aria-live polite was added for a good reason, although it likely lead to reading too much.

Are we sure this PR doesn't revert the fix we made (where initially it didn't always announce).

See my comment here: #8174 (comment)

[slorber]

Would appreciate it if skilled a11y devs can help figure out if this is an improvement or not 😄

cc @BenDMyers @JoshuaKGoldberg @zmrhaljiri @timveld

[proke03]

Thanks for your comment.

Maybe it's a bug in nvda.
nvaccess/nvda#10548

The exact cause cannot be determined. However, in the test link, both nvda and screen reader work well.