FIX #606, correct URL for categories if Blog is on /home #630

Job	Run time
CI / Generate matrix	12s
CI / Context	1s
CI / Check governance	0s
CI / 8.1 prf-low mysql57 phpunit blog	2m 38s
CI / 8.2 mariadb phpunit blog	2m 3s
CI / 8.3 mysql80 phpunit blog	2m 7s
CI / 8.3 mysql84 phpunit blog	2m 4s
CI / 8.1 mysql57 phplinting	2m 11s
CI / 8.1 mysql57 endtoend root	3m 49s
CI / 8.3 mysql80 endtoend root	5m 7s
CI / 8.1 mysql57 js	4m 17s
CI / Dispatch tag patch release	0s
	24m 29s

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