Refactor tests to not use mocked class

[KiOui]

Context

• Some tests created in PC-46 used a mocked version of the Search_Engines_Discouraged_Watcher.

Summary

This PR can be summarized in the following changelog entry:

• Changes tests for Search_Engines_Discouraged_Watcher to not use a mocked version of the class.

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:

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

• [x] 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

• [x] I have tested this code to the best of my abilities
• [x] 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.

Fixes PC-347