Add PHPUnit 13 support #66

Job	Run time
analyse	19s
test (8.0)	11s
test (8.5)	11s
test (8.3)	11s
test (8.4)	11s
test (7.4)	11s
test (7.3)	15s
test (7.0, --prefer-stable --prefer-lowest)	34s
test (8.1)	13s
test (7.1)	12s
test (8.2)	14s
test (7.2)	10s
	2m 52s

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