Fix staking benchmark #5805

Job	Run time
preflight / preflight	45s
preflight / ci-versions	57s
test-full-crypto-feature	2m 34s
cargo-check-benches (master)	20m 52s
cargo-check-benches (current)	21m 42s
cargo-check-all-crate-macos	11m 16s
cargo-check-each-crate (1)	18m 25s
cargo-check-each-crate (2)	19m 24s
test-frame-ui	46m 24s
cargo-check-each-crate (3)	9m 34s
test-node-metrics	8m 22s
cargo-check-each-crate (4)	16m 56s
cargo-check-each-crate (5)	24m 5s
cargo-check-each-crate (6)	14m 52s
cargo-check-each-crate (7)	30m 23s
test-frame-examples-compile-to-wasm	3m 11s
test-deterministic-wasm	6m 33s
check-tracing	2m 22s
check-metadata-hash	6m 31s
node-bench-regression-guard	15s
All test misc tests passed	1s
	4h 25m 24s

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