Fix network page of dashboard

[leonidasmi]

Context

Summary

This PR can be summarized in the following changelog entry:

• Fixes an unreleased bug where the general page of the network admin would be broken

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:

• Install Yoast SEO in a multisite
• Visit the network's Yoast SEO general page (/wp-admin/network/admin.php?page=wpseo_dashboard)
• Confirm that it looks as it should
• Visit the Yoast SEO general page in a subsite or in a single site installation
• Confirm that it looks as it should and smoke test it a bit
• Do the same with the new dashboard feature flag both enabled and disabled

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
• [x] Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• [x] QA should use the same steps as above.

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

• [x] 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.
• [x] If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• [x] I have written this PR in accordance with my team's definition of done.
• [x] 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 7fc2ca6f184fde5c83e457fc26f0ffe301192844

Details

• 5 of 6 (83.33%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+5.2%) to 54.569%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
admin/class-config.php	0	1	0.0%
<!--	Total:	5	6

Totals
Change from base Build ad2c4b607f7daae862318f3d8e622f745e25b2c7:	5.2%
Covered Lines:	29678
Relevant Lines:	54656

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💛 - Coveralls

[hardikgohil7988]

Tested new dashboard in multisite.