Remove evals from pattern-matching spec #1608

Job	Run time
RuboCop	6s
specs (ubuntu, 3.0.6)	1m 3s
specs (ubuntu, 3.1.4)	1m 27s
specs (ubuntu, 3.2.2)	1m 24s
specs (ubuntu, 3.3.0)	1m 24s
specs (macos, 3.0.6)	1m 6s
specs (macos, 3.1.4)	1m 32s
specs (macos, 3.2.2)	1m 8s
specs (macos, 3.3.0)	1m 9s
specs (windows, 3.0.6)	3m 31s
specs (windows, 3.1.4)	3m 36s
specs (windows, 3.2.2)	3m 31s
specs (windows, 3.3.0)	3m 30s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 27s
	25m 54s

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