API Update API to reflect changes in silverstripe/cms #599

Job	Run time
CI / Context	1s
CI / Generate matrix	1m 12s
CI / 8.3 prf-low mariadb phpunit blog	2m 38s
CI / Check governance	0s
CI / 8.3 mysql80 phpunit blog	2m 34s
CI / 8.4 mysql84 phpunit blog	2m 10s
CI / 8.3 mysql80 phplinting	1m 50s
CI / 8.3 mysql80 endtoend root	5m 14s
CI / 8.4 mysql84 endtoend root	4m 18s
CI / 8.3 mysql80 js	3m 44s
CI / Dispatch tag patch release	0s
	23m 41s

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