Update descriptions for rational exponent for Ruby 3.4 #1848

Job	Run time
RuboCop	33s
specs (ubuntu, 3.0.6)	1m 30s
specs (ubuntu, 3.1.4)	1m 34s
specs (ubuntu, 3.2.2)	1m 26s
specs (ubuntu, 3.3.0)	1m 25s
specs (macos, 3.0.6)	1m 19s
specs (macos, 3.1.4)	1m 21s
specs (macos, 3.2.2)	1m 10s
specs (macos, 3.3.0)	1m 10s
specs (windows, 3.0.6)	4m 28s
specs (windows, 3.1.4)	4m 17s
specs (windows, 3.2.2)	4m 16s
specs (windows, 3.3.0)	4m 29s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 26s
	30m 24s

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