Fix false positive for files with only require_once and class definitions

[GeorgeWebDevCy]

Fixes #1361

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Co-authored-by: GeorgeWebDevCy <orionaselite@git.wordpress.org>
Co-authored-by: davidperezgar <davidperez@git.wordpress.org>
Co-authored-by: ernilambar <nilambar@git.wordpress.org>
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[davidperezgar]

Thanks @GeorgeWebDevCy for your contribution. You need to review the tests that are failing before we can review the PR.

[GeorgeWebDevCy]

Thanks for the heads up. I reviewed the failing tests and pushed a follow-up fix in 3813175. The CI matrix is now passing.

[ernilambar]

Why this change?

[GeorgeWebDevCy]

This updates the input name for the pinned Codecov action. At commit fb8b3582c8e4def4969c97caa2f19720cb33a72f, the action defines files (a comma-separated list of explicit coverage files) and passes it through as INPUT_FILES; it does not define a file input. Both occurrences use the same build/logs/*.xml pattern, so this makes the workflow use the action's supported input without changing which reports we intend to upload.