Bump to actions/checkout@v4 #555

Job	Run time
Code coverage (codecov)	24s
CI test (make validate)	27s
Integration tests (8.2, main)	6m 3s
Build moodle-plugin-ci.phar	36s
Integration tests (8.2, MOODLE_403_STABLE)	5m 58s
Integration tests (8.2, MOODLE_402_STABLE)	5m 54s
Integration tests (8.1, MOODLE_401_STABLE)	6m 44s
Integration tests (8.0, MOODLE_400_STABLE)	6m 40s
Integration tests (8.0, MOODLE_311_STABLE)	5m 54s
Integration tests (7.4, MOODLE_39_STABLE)	6m 0s
Integration tests (PHAR) (8.2, main)	6m 23s
Integration tests (PHAR) (8.1, MOODLE_403_STABLE)	5m 42s
Integration tests (PHAR) (8.0, MOODLE_401_STABLE)	6m 32s
Integration tests (PHAR) (7.4, MOODLE_400_STABLE)	5m 39s
	1h 8m 56s

Provide feedback