Bump json from 2.6.3 to 2.7.2 in /steep #4788

Job	Run time
test (3.0, test)	1m 52s
test (3.1, test)	2m 2s
windows (windows-2019, ucrt)	44s
windows (windows-2019, mswin)	1m 9s
test (3.2, test)	2m 4s
test (3.3, test)	2m 13s
windows (windows-2022, ucrt)	1m 21s
windows (windows-2022, mswin)	1m 43s
test (head, test)	2m 1s
test (head, stdlib_test rubocop)	1m 49s
test (3.3, stdlib_test)	2m 13s
test (3.3, test, --enable-frozen-string-literal)	2m 17s
test (3.3, stdlib_test, --enable-frozen-string-literal)	2m 25s
test (3.3, lexer compile confirm_lexer)	3m 5s
test (3.3, rubocop validate test_doc build test_generate_stdlib raap)	2m 24s
	29m 22s

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