ENH Update code to reflect changes to silverstripe/admin #1050

Job	Run time
CI / Generate matrix	12s
CI / Context	1s
CI / Check governance	0s
CI / 8.3 prf-low mariadb phpunit all	2m 51s
CI / 8.3 mysql80 phpunit all	2m 56s
CI / 8.3 mysql84 phpunit all	3m 4s
CI / 8.3 mysql80 phplinting	1m 44s
CI / 8.3 mysql80 endtoend root job1	9m 2s
CI / 8.3 mysql80 endtoend root job2	9m 19s
CI / 8.3 mysql80 endtoend root job3	7m 37s
CI / 8.3 mysql80 js	4m 24s
CI / Dispatch tag patch release	0s
	41m 10s

Provide feedback