Ruby

Remove StringScanner methods absent from the latest Ruby release #8147

Job	Run time
C99_compile (head)	49s
C99_compile (4.0)	1m 7s
clang_compile (head)	47s
clang_compile (4.0)	1m 12s
test (3.2, test)	2m 8s
test (4.0, stdlib_test)	1m 48s
test (asan-release, test)	7m 51s
test (3.4, test)	2m 13s
test (head, stdlib_test rubocop)	1m 59s
test (4.0, test)	2m 14s
test (4.0, test, --enable-frozen-string-literal)	2m 22s
test (4.0, typecheck_test)	1m 14s
test (4.0, rubocop validate test_doc build test_generate_stdlib raap)	2m 36s
test (4.0, stdlib_test, --enable-frozen-string-literal)	1m 50s
test (3.3, test)	2m 22s
test (head, test)	2m 1s
	34m 33s

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