remove pallet::getter from pallet-staking #5796

Job	Run time
preflight / preflight	40s
preflight / ci-versions	54s
cargo-check-benches (master)	21m 6s
cargo-check-benches (current)	25m 8s
test-frame-ui	46m 23s
cargo-check-each-crate (1)	26m 59s
cargo-check-each-crate (2)	23m 15s
cargo-check-each-crate (3)	9m 21s
test-node-metrics	12m 18s
cargo-check-each-crate (4)	23m 35s
cargo-check-each-crate (5)	32m 6s
cargo-check-all-crate-macos	11m 10s
cargo-check-each-crate (6)	16m 14s
test-full-crypto-feature	2m 40s
cargo-check-each-crate (7)	32m 28s
test-frame-examples-compile-to-wasm	3m 7s
test-deterministic-wasm	8m 7s
check-tracing	2m 40s
check-metadata-hash	7m 10s
node-bench-regression-guard	13s
All test misc tests passed	1s
	5h 5m 35s

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