Upgrade benchmarks to Rails 8.1 #1569

Job	Run time
benchmark-ractor-only (head)	38s
benchmark-run-once	1m 22s
benchmark-graph	1m 0s
benchmark-default (head)	12m 20s
test (head)	1m 20s
test (ruby)	1m 6s
benchmark-default (ruby)	11m 42s
benchmark-ractor (head)	6m 52s
test (truffleruby)	1m 3s
benchmark-default (truffleruby)	14m 59s
all-tests	3s
	52m 25s

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