Drop 3.2 support in ruby/spec #2307

Job	Run time
RuboCop	42s
specs (ubuntu, 4.0.1, --repeat 2)	2m 20s
specs (ubuntu, 4.0.1, --enable-frozen-string-literal)	1m 31s
specs (ubuntu, 3.3.10)	1m 29s
specs (ubuntu, 4.0.1)	1m 35s
specs (macos, 4.0.1)	1m 30s
specs (windows, 4.0.1)	3m 23s
specs (ubuntu, 3.4.8)	1m 39s
specs (macos, 3.4.8)	1m 33s
specs (windows, 3.4.8)	3m 23s
specs (macos, 3.3.10)	1m 29s
specs (windows, 3.3.10)	3m 33s
specs (ubuntu, 4.0.1, --parser=parse.y)	1m 45s
	25m 52s

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