test

Bump rbs from v3.5.3 to v3.6.0 and steep from v1.7.1 to v1.8.0 #1405

Job	Run time
test-memory (head)	36s
test-ruby (head, master)	5m 54s
check-misc (head)	12s
steep-check (head)	28s
test-ruby (3.0, master)	5m 49s
test-windows (head)	2m 34s
ruby-versions / Generate Ruby versions	3s
test-cpp (head, g++)	13s
test (2.5)	24s
test-cpp (head, clang++)	19s
test (2.6)	30s
test (2.7)	26s
test (3.0)	26s
test (3.1)	19s
test (3.2)	13s
test (3.3)	13s
test (head)	11s
	18m 50s

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