Update README.md #1669

Job	Run time
RuboCop	24s
specs (ubuntu, 3.0.6)	1m 31s
specs (ubuntu, 3.1.4)	1m 30s
specs (ubuntu, 3.2.2)	1m 28s
specs (ubuntu, 3.3.0)	1m 26s
specs (macos, 3.0.6)	1m 21s
specs (macos, 3.1.4)	1m 21s
specs (macos, 3.2.2)	1m 18s
specs (macos, 3.3.0)	1m 12s
specs (windows, 3.0.6)	3m 26s
specs (windows, 3.1.4)	4m 34s
specs (windows, 3.2.2)	4m 35s
specs (windows, 3.3.0)	4m 59s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 26s
	30m 31s

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