Simplify `Enumerable#to_a` #13440

Job	Run time
check_format	1m 36s
x86_64-gnu-test-preview_mt	5m 55s
x86_64-gnu-test (1.7.3)	32m 57s
x86_64-musl-test	36m 53s
x86_64-gnu-test (1.8.2)	35m 6s
x86_64-gnu-test (1.9.2)	33m 31s
x86_64-gnu-test (1.10.1)	34m 12s
x86_64-gnu-test (1.11.2)	33m 4s
x86_64-gnu-test (1.12.2)	32m 18s
x86_64-gnu-test (1.13.3)	33m 35s
x86_64-gnu-test (1.14.1)	32m 41s
x86_64-gnu-test (1.15.1)	34m 40s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	34m 33s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	33m 27s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	34m 19s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	34m 51s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	34m 33s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	34m 26s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	32m 26s
	9h 45m 3s

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