Add tests for the indexables-pages slice of llms.txt

[igorschoester]

Context

Summary

This PR can be summarized in the following changelog entry:

• Adds tests for the indexables-pages slice of llms.txt.

Relevant technical choices:

• see commits and messages

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

Devs:

• Run the JS test suite with code coverage: yarn workspace @yoast/wordpress-seo jest --coverage "tests/settings/store/indexable-pages.test.js"
• Verify it has 100% coverage (though not 100% branches, too many safety checks)

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:

• Tests, and 1 dependency array addition that is so standard there is no need.

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 2b704a025393e64c6a6fded2682ea29ba7b063ce

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 64 unchanged lines in 5 files lost coverage.
• Overall coverage increased (+0.4%) to 53.669%

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Files with Coverage Reduction	New Missed Lines	%
packages/js/src/settings/helpers/search.js	6	15.0%
packages/js/src/settings/store/index.js	6	0.0%
packages/js/src/settings/routes/site-features.js	13	0.0%
packages/js/src/settings/app.js	15	0.0%
packages/js/src/settings/initialize.js	24	0.0%

Totals
Change from base Build f84a8ac44b0411b1a4b1db1c6c4fff6b506aff62:	0.4%
Covered Lines:	30553
Relevant Lines:	57926

---

💛 - Coveralls

[leonidasmi]

CR and acceptance is ✅