Add copy and shortlink in feature card

[leonidasmi]

Context

Summary

This PR can be summarized in the following changelog entry:

• Adds the proper copy and shortlink in the feature card.
• Disables the feature for multisites.

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:

• Go to Yoast SEO -> Settings and confirm that the copy is like this:

LLMs.txt

Boost the visibility of your content in AI searches. Automatically create an llms.txt file that lists a selection of your site’s content. This helps LLMs access and provide your site's information more easily.

View llms.txt

• Confirm that the shortlink in the Learn more is this: https://yoa.st/site-features-llmstxt-learn-more

Also:

• Install the PR/RC in a fresh multisite installation
• Confirm that in the Yoast settings, you see the below:
  
• Using WP Crontrol, confirm there's no wpseo_llms_txt_population action
• Confirm that there's no llms.txt file
• In the network Yoast settings, you see no feature toggle for the LLMs.txt feature
  • Enable and disable some of those network Yoast settings
  • Enable and disable some of the Yoast settings in a subsite
  • Make sure things work as expected and that you still dont see no llms.txt file and no wpseo_llms_txt_population action and the LLMs.txt setting is still disabled in Yoast settings in subsites.

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 (Default Block/Gutenberg/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.

Impact check

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

• Multisite Yoast settings

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. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

• I have tested this code to the best of my abilities.
• During testing, I had activated all plugins that Yoast SEO provides integrations for.
• 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.
• I have checked that the base branch is correctly set.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label.
• I have added my hours to the WBSO document.

Fixes https://github.com/Yoast/reserved-tasks/issues/565

[coveralls]

Pull Request Test Coverage Report for Build 99fa54dc86a0fb60f3008ee12b1ac1f4085beef5

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.5%) to 52.847%

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Totals
Change from base Build 84224945dc8a5d9b43d7a0ba0c1516c0cb20c65c:	0.5%
Covered Lines:	29656
Relevant Lines:	57352

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💛 - Coveralls

[thijsoo]

LGTM 👍