DEP Increase minimum version of silverstripe/framework #479

Job	Run time
CI / Generate matrix	21s
CI / Context	1s
CI / 8.1 prf-low mysql57 phpunit all	2m 11s
CI / Check governance	0s
CI / 8.2 mariadb phpunit all	2m 16s
CI / 8.3 mysql80 phpunit all	2m 37s
CI / 8.1 mysql57 phplinting	2m 12s
CI / 8.1 mysql57 endtoend root	3m 41s
CI / 8.3 mysql80 endtoend root	4m 43s
CI / 8.1 mysql57 js	4m 25s
CI / Dispatch tag patch release	0s
	22m 27s

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