Remove evals from pattern-matching spec #1607

Job	Run time
RuboCop	28s
specs (ubuntu, 3.0.6)	1m 0s
specs (ubuntu, 3.1.4)	1m 31s
specs (ubuntu, 3.2.2)	1m 23s
specs (ubuntu, 3.3.0)	1m 22s
specs (macos, 3.0.6)	1m 12s
specs (macos, 3.1.4)	1m 47s
specs (macos, 3.2.2)	1m 25s
specs (macos, 3.3.0)	2m 43s
specs (windows, 3.0.6)	5m 2s
specs (windows, 3.1.4)	4m 59s
specs (windows, 3.2.2)	5m 2s
specs (windows, 3.3.0)	5m 0s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 22s
	34m 16s

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