Bump rbs from v3.6.0 to v3.7.0 and steep from v1.8.0 to v1.8.1 #1434

Job	Run time
check-misc (head)	7s
steep-check (head)	13s
test-memory (head)	39s
test-ruby (head, master)	5m 57s
test-ruby (3.0, master)	6m 13s
test-windows (head)	1m 45s
ruby-versions / Generate Ruby versions	4s
test-cpp (head, g++)	15s
test (2.5)	24s
test-cpp (head, clang++)	20s
test (2.6)	29s
test (2.7)	29s
test (3.0)	11s
test (3.1)	15s
test (3.2)	14s
test (3.3)	14s
test (head)	17s
	18m 6s

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