Cleanup shared/enumerator #1854

Job	Run time
RuboCop	30s
specs (ubuntu, 3.0.6)	1m 31s
specs (ubuntu, 3.1.4)	1m 29s
specs (ubuntu, 3.2.2)	1m 23s
specs (ubuntu, 3.3.0)	1m 23s
specs (macos, 3.0.6)	1m 20s
specs (macos, 3.1.4)	1m 19s
specs (macos, 3.2.2)	1m 8s
specs (macos, 3.3.0)	1m 9s
specs (windows, 3.0.6)	4m 16s
specs (windows, 3.1.4)	4m 0s
specs (windows, 3.2.2)	4m 51s
specs (windows, 3.3.0)	4m 39s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 26s
	30m 24s

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