Ruby

Update the target Ruby version notes to the latest release #8149

Job	Run time
clang_compile (head)	1m 3s
C99_compile (4.0)	49s
C99_compile (head)	51s
test (head, test)	2m 3s
test (3.3, test)	2m 35s
test (4.0, stdlib_test)	1m 49s
test (3.4, test)	2m 20s
test (head, stdlib_test rubocop)	1m 42s
test (4.0, test, --enable-frozen-string-literal)	2m 23s
test (4.0, typecheck_test)	1m 17s
test (4.0, test)	2m 18s
test (asan-release, test)	7m 56s
clang_compile (4.0)	1m 4s
test (4.0, rubocop validate test_doc build test_generate_stdlib raap)	2m 32s
test (3.2, test)	2m 9s
test (4.0, stdlib_test, --enable-frozen-string-literal)	1m 57s
	34m 48s

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