Tests: use PHPUnit annotations

[jrfnl]

Summary

This PR can be summarized in the following changelog entry:

• Test tweak

Relevant technical choices:

Use PHPUnit annotations instead of properties.

Apparently this must have worked in some way, but the preserveGlobalState for the DependencyYoastSEOTest was definitely not correct (and probably not working either).

Test instructions

This PR can be tested by following these steps:

• N/A If the builds pass, we're good.

[coveralls]

Pull Request Test Coverage Report for Build 6925892474

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A quick fix for this PR: rebase it; your next report should be accurate.

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 56.274%

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Totals
Change from base Build 6925868219:	0.0%
Covered Lines:	148
Relevant Lines:	263

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💛 - Coveralls