Fix JSON_OBJECT_AS_ARRAY flag documentation #2019

Job	Run time
Run cs-fixer and stubs structure tests	3m 3s
Run tests against php 5.6	12m 0s
Run tests against php 7.0	11m 28s
Run tests against php 7.1	12m 21s
Run tests against php 7.2	13m 18s
Run tests against php 7.3	14m 0s
Run tests against php 7.4	13m 25s
Run tests against php 8.0	8s
Run tests against php 8.1	15m 31s
Run tests against php 8.2	17m 49s
Run tests against php 8.3	15m 59s
	2h 9m 2s

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