Add specs for Process::Status#>> #318

Job	Run time
RuboCop	29s
specs (ubuntu, 3.0.6)	1m 32s
specs (ubuntu, 3.1.4)	1m 34s
specs (ubuntu, 3.2.2)	1m 29s
specs (ubuntu, 3.3.0)	1m 26s
specs (macos, 3.0.6)	1m 19s
specs (macos, 3.1.4)	1m 36s
specs (macos, 3.2.2)	1m 9s
specs (macos, 3.3.0)	1m 7s
specs (windows, 3.0.6)	3m 45s
specs (windows, 3.1.4)	4m 39s
specs (windows, 3.2.2)	4m 44s
specs (windows, 3.3.0)	4m 36s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 28s
	30m 53s

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