remove exit-future #15472

Job	Run time
cargo-udeps	7m 0s
check-code	10m 10s
beacon-chain-tests	18m 22s
check-msrv	4m 27s
cli-check	18m 43s
compile-with-beta-compiler	14m 18s
debug-tests-ubuntu	14m 57s
dockerfile-ubuntu	13m 47s
doppelganger-protection-test	25m 46s
ef-tests-ubuntu	14m 3s
eth1-simulator-ubuntu	30m 11s
execution-engine-integration-ubuntu	15m 1s
merge-transition-ubuntu	29m 49s
network-tests	17m 15s
no-eth1-simulator-ubuntu	28m 2s
op-pool-tests	20m 42s
release-tests-ubuntu	17m 57s
release-tests-windows	25m 27s
slasher-tests	5m 27s
state-transition-vectors-ubuntu	11m 59s
syncing-simulator-ubuntu	22m 11s
target-branch-check	1s
test-suite-success	8s
	6h 5m 43s

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