refactor: simplify EveryTestHasSameNamespaceAsCoveredClass check

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.50 :tada:

Comparison is base (fadd7ed) 97.82% compared to head (5d04fe4) 98.33%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #71 +/- ## ============================================ + Coverage 97.82% 98.33% +0.50% + Complexity 52 51 -1 ============================================ Files 6 6 Lines 184 180 -4 ============================================ - Hits 180 177 -3 + Misses 4 3 -1 ``` | [Impacted Files](https://codecov.io/gh/cdn77/TestUtils/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cdn77) | Coverage Δ | | |---|---|---| | [...tCheck/EveryTestHasSameNamespaceAsCoveredClass.php](https://codecov.io/gh/cdn77/TestUtils/pull/71?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cdn77#diff-c3JjL1Rlc3RDaGVjay9FdmVyeVRlc3RIYXNTYW1lTmFtZXNwYWNlQXNDb3ZlcmVkQ2xhc3MucGhw) | `97.36% <100.00%> (+2.13%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cdn77). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cdn77)

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