Add RBS for `::DATA` #3246

Job	Run time
windows (windows-2019, ucrt)	1m 37s
windows (windows-2019, mswin)	1m 13s
windows (windows-2022, ucrt)	1m 38s
windows (windows-2022, mswin)	2m 1s
test (master-nightly-focal, test)	2m 4s
test (master-nightly-focal, stdlib_test)	3m 6s
test (master-nightly-focal, rubocop validate test_doc build test_generate_stdlib)	2m 16s
test (master-nightly-focal, lexer confirm_lexer)	3m 57s
test (master-nightly-focal, lexer compile)	4m 44s
test (3.2-dev-focal, test)	2m 1s
test (3.2-dev-focal, stdlib_test)	2m 9s
test (3.2-dev-focal, rubocop validate test_doc build test_generate_stdlib)	2m 36s
test (3.2-dev-focal, lexer confirm_lexer)	3m 59s
test (3.2-dev-focal, lexer compile)	4m 1s
test (3.1-dev-focal, test)	2m 53s
test (3.1-dev-focal, rubocop validate test_doc build test_generate_stdlib)	2m 18s
test (3.1-dev-focal, lexer confirm_lexer)	4m 2s
test (3.1-dev-focal, lexer compile)	4m 0s
test (3.0-dev-focal, test)	2m 6s
test (3.0-dev-focal, rubocop validate test_doc build test_generate_stdlib)	2m 52s
test (3.0-dev-focal, lexer confirm_lexer)	4m 4s
test (3.0-dev-focal, lexer compile)	4m 1s
	1h 3m 38s

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