Disable llms.txt setting in multisites

[leonidasmi]

Context

Summary

This PR can be summarized in the following changelog entry:

• Disables the llms.txt setting for multisites in the new settings page too.

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 a fresh multisite and install Yoast SEO
• Go to the main subsite's Yoast settings page and confirm that the llms.txt feature toggle is disabled both in the Site features page and in the llms.txt settings page and you can't enable the feature
• Save a random different setting, refresh and confirm that you still see the llms.txt feature as disabled
• Repeat the same in a subsite that's not the main one

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.

QA can test this PR by following these steps:

• The above, plus:
• Repeat the same in a multisite that had Yoast SEO already and got upgraded to this RC/PR.

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. 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 #

[coveralls]

Pull Request Test Coverage Report for Build 24a9a73a2a25e3e0924a01d5e6a08671fc7b75b9

Details

• 0 of 1 (0.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.001%) to 53.726%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/js/src/settings/routes/llms-txt.js	0	1	0.0%

Totals
Change from base Build cf738c03849c0304682f7fda590e4d2ed320011e:	-0.001%
Covered Lines:	30488
Relevant Lines:	57715

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💛 - Coveralls

[vraja-pro]

CR & AC ✅