Remove evals from pattern-matching spec #1617

Job	Run time
RuboCop	25s
specs (ubuntu, 3.0.6)	1m 29s
specs (ubuntu, 3.1.4)	1m 29s
specs (ubuntu, 3.2.2)	1m 26s
specs (ubuntu, 3.3.0)	1m 27s
specs (macos, 3.0.6)	1m 21s
specs (macos, 3.1.4)	1m 22s
specs (macos, 3.2.2)	1m 11s
specs (macos, 3.3.0)	1m 11s
specs (windows, 3.0.6)	5m 41s
specs (windows, 3.1.4)	4m 27s
specs (windows, 3.2.2)	6m 24s
specs (windows, 3.3.0)	5m 26s
specs (ubuntu, 3.3.0, --enable-frozen-string-literal)	1m 26s
	34m 45s

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