MNT Resolve deprecation warning in test #574

Job	Run time
CI / Generate matrix	37s
CI / Generate matrix	37s
CI / Context	1s
CI / Context	1s
CI / Check governance	0s
CI / Check governance	0s
CI / 8.1 prf-low mysql57 phpunit all	2m 48s
CI / 8.1 prf-low mysql57 phpunit all	2m 48s
CI / 8.2 mariadb phpunit all	3m 14s
CI / 8.2 mariadb phpunit all	3m 14s
CI / 8.3 mysql80 phpunit all	3m 3s
CI / 8.3 mysql80 phpunit all	3m 3s
CI / 8.1 mysql57 phplinting	1m 47s
CI / 8.1 mysql57 phplinting	1m 47s
CI / 8.1 mysql57 endtoend asset-admin	4m 20s
CI / 8.1 mysql57 endtoend asset-admin	21m 10s
CI / 8.1 mysql57 endtoend versioned-admin	9m 16s
CI / 8.1 mysql57 endtoend versioned-admin	9m 16s
CI / 8.1 mysql57 endtoend silverstripe-elemental	31m 31s
CI / 8.1 mysql57 endtoend silverstripe-elemental	31m 31s
CI / Dispatch tag patch release	0s
CI / Dispatch tag patch release	0s
	2h 10m 4s

Provide feedback