Bump cross-spawn from 7.0.3 to 7.0.6 #800

Job	Run time
CI / Generate matrix	12s
CI / Context	1s
CI / 8.1 prf-low mysql57 phpunit all	4m 13s
CI / Check governance	0s
CI / 8.2 mariadb phpunit all	3m 37s
CI / 8.3 mysql80 phpunit all	4m 41s
CI / 8.3 mysql84 phpunit all	4m 19s
CI / 8.1 mysql57 phplinting	1m 49s
CI / 8.1 mysql57 endtoend root	5m 21s
CI / 8.3 mysql80 endtoend root	5m 15s
CI / 8.1 mysql57 js	4m 42s
CI / 8.1 mysql57 doclinting	2m 25s
CI / Dispatch tag patch release	0s
	36m 35s

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