Use general stylelint task in grunt command #703

Job	Run time
CI test (make validate)	1m 1s
Code coverage (codecov)	59s
Build moodle-plugin-ci.phar	42s
Integration tests (8.3, main, true)	6m 40s
Integration tests (8.3, MOODLE_404_STABLE, true)	6m 26s
Integration tests (8.2, MOODLE_403_STABLE, true)	6m 12s
Integration tests (8.2, MOODLE_402_STABLE, true)	6m 11s
Integration tests (8.1, MOODLE_401_STABLE, true)	6m 42s
Integration tests (8.0, MOODLE_400_STABLE)	5m 38s
Integration tests (8.0, MOODLE_311_STABLE)	5m 20s
Integration tests (7.4, MOODLE_39_STABLE)	4m 52s
SelfUpdate tests (PHAR) (8.3)	32s
Integration tests (PHAR) (8.3, main, true)	5m 43s
SelfUpdate tests (PHAR) (8.2)	29s
Integration tests (PHAR) (8.3, MOODLE_404_STABLE, true)	5m 54s
SelfUpdate tests (PHAR) (8.1)	18s
Integration tests (PHAR) (8.2, MOODLE_403_STABLE, true)	5m 58s
SelfUpdate tests (PHAR) (8.0)	22s
Integration tests (PHAR) (8.1, MOODLE_402_STABLE, true)	5m 26s
SelfUpdate tests (PHAR) (7.4)	8s
Integration tests (PHAR) (8.0, MOODLE_401_STABLE, true)	6m 10s
Integration tests (PHAR) (7.4, MOODLE_400_STABLE)	4m 57s
	1h 26m 40s

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