Update pyproject-fmt to 2.15.2

[adamtheturtle]

Update pyproject-fmt to 2.15.2.

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Note

Low Risk
Low risk dependency version bump limited to test tooling requirements.

Overview
Updates test-requirements.txt to bump pyproject-fmt from 2.8.0 to 2.15.2.

^{Written by Cursor Bugbot for commit f41c533. This will update automatically on new commits. Configure here.}