Remove evals from pattern-matching spec #1609

Job	Run time
RuboCop	27s
specs (ubuntu, 3.0.6)	1m 1s
specs (ubuntu, 3.1.4)	1m 32s
specs (ubuntu, 3.2.2)	1m 25s
specs (ubuntu, 3.3.0)	1m 26s
specs (macos, 3.0.6)	1m 25s
specs (macos, 3.1.4)	1m 21s
specs (macos, 3.2.2)	1m 15s
specs (macos, 3.3.0)	1m 36s
specs (windows, 3.0.6)	1m 37s
specs (windows, 3.1.4)	1m 40s
specs (windows, 3.2.2)	1m 40s
specs (windows, 3.3.0)	1m 38s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 24s
	19m 27s

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