API Update API to reflect changes in silverstripe/cms #604

Job	Run time
CI / Context	1s
CI / Generate matrix	26s
CI / Check governance	0s
CI / 8.3 prf-low mariadb phpunit blog	2m 20s
CI / 8.3 mysql80 phpunit blog	1m 51s
CI / 8.4 mysql84 phpunit blog	1m 38s
CI / 8.3 mysql80 phplinting	1m 41s
CI / 8.3 mysql80 endtoend root	3m 52s
CI / 8.4 mysql84 endtoend root	2m 40s
CI / 8.3 mysql80 js	1m 49s
CI / Dispatch tag patch release	0s
	16m 18s

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