Revise Siren documentation #18930

Job	Run time
Check for 'skip-ci' label	1s
lockbud	1m 56s
check-msrv	2m 6s
check-code	2m 33s
target-branch-check	1s
op-pool-tests	2m 1s
beacon-chain-tests	2m 2s
release-tests-ubuntu	2m 2s
network-tests	2m 32s
release-tests-windows	1m 46s
basic-simulator-ubuntu	2m 0s
cargo-udeps	2m 0s
cli-check	1m 59s
compile-with-beta-compiler	2m 3s
debug-tests-ubuntu	2m 1s
ef-tests-ubuntu	2m 2s
execution-engine-integration-ubuntu	2m 2s
fallback-simulator-ubuntu	2m 17s
slasher-tests	1m 48s
state-transition-vectors-ubuntu	2m 0s
test-suite-success	1s
	37m 13s

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