Fix the NotificationToast isVisible issue and increase duration

[amelako]

Purpose

Based on how fast the average American reads, a good lenght of time to keep the toast message up is 5 seconds plus 1 extra second for every 120 words.
The shortest default that should be used as a best practice is 6 seconds.

Approach and changes

Increased the toast duration to 6 seconds.

Definition of done

• Development completed
• Reviewers assigned
• Unit and integration tests
• Meets minimum browser support
• Meets accessibility requirements

[sumup-clark]

Hey @amelako,
we are super excited that you are contributing! 🎉There's one more thing you need to do. Please accept our Contributor License Agreement. It helps you and us to collaborate on clear terms and focus on what we love most: code.

Thanks!

[changeset-bot]

🦋 Changeset detected

Latest commit: 209dc87

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sumup/circuit-ui	Patch

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[vercel]

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🔍 Inspect: https://vercel.com/sumup/oss-circuit-ui/HEJhNoch1S7HxMCLKAWjXPgS1Q6v
✅ Preview: https://oss-circuit-ui-git-toast-a11y-bugfix-sumup.vercel.app

[codecov]

Codecov Report

Merging #1357 (209dc87) into main (681d43e) will increase coverage by 0.00%.
The diff coverage is 60.00%.

@@           Coverage Diff           @@
##             main    #1357   +/-   ##
=======================================
  Coverage   92.19%   92.19%           
=======================================
  Files         190      190           
  Lines        3780     3782    +2     
  Branches     1175     1209   +34     
=======================================
+ Hits         3485     3487    +2     
+ Misses        277      276    -1     
- Partials       18       19    +1     

Impacted Files	Coverage Δ
...components/NotificationToast/NotificationToast.tsx	88.88% <0.00%> (-2.03%)	⬇️
...ircuit-ui/components/ToastContext/ToastContext.tsx	92.30% <66.66%> (+0.20%)	⬆️
...rcuit-ui/components/ToastContext/createUseToast.ts	100.00% <100.00%> (ø)
...es/circuit-ui/components/Pagination/Pagination.tsx	91.42% <0.00%> (ø)
...mponents/NotificationBanner/NotificationBanner.tsx	83.60% <0.00%> (+1.63%)	⬆️

[robinmetral]

Nothing to add beyond Connor's comment. Thank you!