Doc: correct a statement feature singlethreaded eliminates Send bound #3356

Job	Run time
lint	6m 41s
cluster-benchmark (cluster_benchmark)	51s
examples (stable, memstore)	47s
openraft-feature-test (nightly)	55s
examples (stable, raft-kv-memstore)	2m 16s
openraft-test (stable, 0)	3m 12s
examples (stable, raft-kv-memstore-generic-snapshot-data)	1m 0s
openraft-feature-test (nightly, serde)	54s
openraft-test-bench (nightly)	58s
examples (stable, raft-kv-memstore-opendal-snapshot-data)	1m 28s
openraft-test (nightly, 30)	3m 40s
examples (stable, raft-kv-memstore-singlethreaded)	59s
openraft-feature-test (nightly, single-term-leader)	53s
openraft-test (nightly, 0, single-term-leader)	3m 27s
stores (stores/memstore)	57s
openraft-feature-test (nightly, single-term-leader,serde,singlethreaded)	52s
examples (stable, raft-kv-rocksdb)	8m 42s
stores (stores/rocksstore)	6m 16s
examples (nightly, memstore)	56s
Build (nightly, bench,serde,bt,singlethreaded)	52s
tests-feature-test (nightly)	3m 3s
examples (nightly, raft-kv-memstore)	2m 18s
stores (stores/sledstore)	1m 7s
examples (nightly, raft-kv-memstore-generic-snapshot-data)	1m 18s
tests-feature-test (nightly, single-term-leader)	3m 11s
examples (nightly, raft-kv-memstore-opendal-snapshot-data)	1m 55s
tests-feature-test (nightly, loosen-follower-log-revert)	3m 10s
examples (nightly, raft-kv-memstore-singlethreaded)	1m 20s
examples (nightly, raft-kv-rocksdb)	13m 3s
	1h 17m 1s

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