Version-guard these specs #1690

Job	Run time
RuboCop	27s
specs (ubuntu, 3.0.6)	1m 28s
specs (ubuntu, 3.1.4)	1m 34s
specs (ubuntu, 3.2.2)	1m 25s
specs (ubuntu, 3.3.0)	1m 26s
specs (macos, 3.0.6)	1m 39s
specs (macos, 3.1.4)	1m 43s
specs (macos, 3.2.2)	1m 13s
specs (macos, 3.3.0)	1m 15s
specs (windows, 3.0.6)	4m 58s
specs (windows, 3.1.4)	5m 15s
specs (windows, 3.2.2)	5m 17s
specs (windows, 3.3.0)	6m 39s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 21s
	35m 40s

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