Dupp 900 introduction modal dialog accessibility

[vraja-pro]

Context

• Related to Fix Introduction modal dialog a11y.
• Please ignore, there is a revert for this Revert "Dupp 900 introduction modal dialog accessibility" #19651.

Summary

This PR can be summarized in the following changelog entry:

• Please ignore, there is a revert for this Revert "Dupp 900 introduction modal dialog accessibility" #19651.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Relates to Fix Introduction modal dialog a11y.

Relevant test scenarios

• Changes should be tested with the browser console open
• Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• Changes should be tested on different editors (Block/Classic/Elementor/other)
• Changes should be tested on different browsers
• Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Other environments

• This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• I have written documentation for this change.

Quality assurance

• I have tested this code to the best of my abilities
• I have added unit tests to verify the code works as intended
• If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• I have written this PR in accordance with my team's definition of done.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label and noted the work hours.

Fixes Fix Introduction modal dialog a11y.

[vraja-pro]

Related to different issue that was CR & ACC ✅