Remove custom SSZ beacon states route #14933

Job	Run time
beacon-chain-tests	3m 26s
cargo-udeps	6m 34s
check-code	6m 31s
check-msrv	4m 13s
cli-check	17m 54s
compile-with-beta-compiler	8m 39s
debug-tests-ubuntu	3m 34s
dockerfile-ubuntu	14m 6s
doppelganger-protection-test	2m 48s
ef-tests-ubuntu	6m 4s
eth1-simulator-ubuntu	10m 40s
execution-engine-integration-ubuntu	1m 18s
merge-transition-ubuntu	10m 46s
network-tests	9m 58s
no-eth1-simulator-ubuntu	10m 59s
op-pool-tests	10m 4s
release-tests-ubuntu	2m 27s
release-tests-windows	4m 34s
slasher-tests	5m 15s
state-transition-vectors-ubuntu	10m 18s
syncing-simulator-ubuntu	10m 37s
target-branch-check	1s
test-suite-success	0s
	2h 40m 46s

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