Update `io.rbs` #3251

Job	Run time
test (master-nightly-focal, test)	2m 9s
test (master-nightly-focal, stdlib_test)	2m 12s
test (master-nightly-focal, rubocop validate test_doc build test_generate_stdlib)	2m 20s
test (master-nightly-focal, lexer confirm_lexer)	4m 51s
test (master-nightly-focal, lexer compile)	4m 3s
test (3.2-dev-focal, test)	2m 11s
test (3.2-dev-focal, stdlib_test)	2m 25s
test (3.2-dev-focal, rubocop validate test_doc build test_generate_stdlib)	2m 12s
test (3.2-dev-focal, lexer confirm_lexer)	4m 59s
test (3.2-dev-focal, lexer compile)	4m 9s
test (3.1-dev-focal, test)	2m 25s
test (3.1-dev-focal, rubocop validate test_doc build test_generate_stdlib)	2m 30s
test (3.1-dev-focal, lexer confirm_lexer)	3m 59s
test (3.1-dev-focal, lexer compile)	4m 0s
test (3.0-dev-focal, test)	2m 29s
test (3.0-dev-focal, rubocop validate test_doc build test_generate_stdlib)	2m 49s
test (3.0-dev-focal, lexer confirm_lexer)	5m 2s
test (3.0-dev-focal, lexer compile)	4m 4s
windows (windows-2019, ucrt)	1m 31s
windows (windows-2019, mswin)	1m 15s
windows (windows-2022, ucrt)	2m 8s
windows (windows-2022, mswin)	2m 0s
	1h 5m 43s

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