ENH Update code to reflect changes to silverstripe/admin #412

Job	Run time
CI / Context	1s
CI / Generate matrix	15s
CI / Check governance	0s
CI / 8.3 prf-low mariadb phpunit all	1m 53s
CI / 8.3 mysql80 phpunit all	2m 9s
CI / 8.4 mysql84 phpunit all	2m 8s
CI / 8.3 mysql80 phplinting	1m 47s
CI / 8.3 mysql80 endtoend root	3m 37s
CI / 8.4 mysql84 endtoend root	3m 51s
CI / 8.3 mysql80 js	4m 10s
CI / Dispatch tag patch release	0s
	19m 51s

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