Doc: add a space #2738

Job	Run time
external-stores (stores/rocksstore-v2)	5m 54s
cluster-benchmark (cluster_benchmark)	46s
examples (stable, raft-kv-memstore)	2m 15s
examples (stable, raft-kv-rocksdb)	7m 54s
lint	6m 39s
examples (nightly, raft-kv-memstore)	2m 3s
openraft-feature-test (nightly)	48s
examples (nightly, raft-kv-rocksdb)	11m 58s
openraft-feature-test (nightly, serde)	52s
openraft-test (stable, 0)	2m 59s
openraft-feature-test (nightly, single-term-leader)	56s
openraft-test (nightly, 30)	3m 7s
openraft-test-bench (nightly)	54s
openraft-feature-test (nightly, single-term-leader,serde,singlethreaded)	53s
openraft-test (nightly, 0, single-term-leader)	3m 1s
Build (nightly, bench,serde,bt,singlethreaded)	50s
stores (memstore)	43s
stores (rocksstore)	5m 55s
tests-feature-test (nightly)	2m 39s
stores (rocksstore-compat07)	6m 21s
tests-feature-test (nightly, single-term-leader)	2m 39s
stores (sledstore)	53s
tests-feature-test (nightly, loosen-follower-log-revert)	2m 41s
	1h 13m 40s

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