tests

Fix errors of phpstan 2.1+ #449

Job	Run time
Tests (8.1, ubuntu-latest, prefer-lowest)	1m 7s
Tests (8.1, ubuntu-latest, prefer-stable)	1m 15s
Tests (8.1, macos-latest, prefer-lowest)	2m 0s
Tests (8.1, macos-latest, prefer-stable)	2m 8s
Tests (8.1, windows-latest, prefer-lowest)	1m 26s
Tests (8.1, windows-latest, prefer-stable)	1m 37s
Tests (8.2, ubuntu-latest, prefer-lowest)	1m 21s
Tests (8.2, ubuntu-latest, prefer-stable)	1m 15s
Tests (8.2, macos-latest, prefer-lowest)	2m 9s
Tests (8.2, macos-latest, prefer-stable)	2m 3s
Tests (8.2, windows-latest, prefer-lowest)	1m 26s
Tests (8.2, windows-latest, prefer-stable)	1m 39s
Tests (8.3, ubuntu-latest, prefer-lowest)	1m 10s
Tests (8.3, ubuntu-latest, prefer-stable)	1m 9s
Tests (8.3, macos-latest, prefer-lowest)	2m 5s
Tests (8.3, macos-latest, prefer-stable)	2m 19s
Tests (8.3, windows-latest, prefer-lowest)	1m 54s
Tests (8.3, windows-latest, prefer-stable)	1m 29s
	29m 32s

Provide feedback