Reset the docs version #975

Job	Run time
Check documentation syntax	13s
Spec - JRuby	2m 28s
Prism	35s
Check the oldest supported RuboCop version	48s
Spec - 3.0	24s
Spec - 2.7	31s
Spec - 3.1	25s
Spec - head	20s
Spec - 3.3	21s
Spec - 4.0	16s
Spec - 3.2	21s
Spec - 3.4	22s
	7m 4s

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