chore: typo in grpc test-cluster.sh #4260

Job	Run time
Build (nightly, bench,serde,bt,singlethreaded)	54s
openraft-test (stable, 0)	3m 19s
openraft-test (nightly, 30)	3m 24s
cluster-benchmark (cluster_benchmark)	48s
openraft-test (nightly, 0, single-term-leader)	3m 15s
examples (stable, memstore)	39s
examples (stable, raft-kv-memstore)	2m 32s
lint	12m 39s
examples (stable, raft-kv-memstore-grpc)	1m 53s
openraft-feature-test (nightly)	50s
examples (stable, raft-kv-memstore-network-v2)	1m 11s
openraft-feature-test (nightly, serde)	59s
examples (stable, raft-kv-memstore-opendal-snapshot-data)	1m 5s
openraft-test-bench (nightly)	1m 0s
examples (stable, raft-kv-memstore-singlethreaded)	49s
openraft-feature-test (nightly, single-term-leader)	50s
examples (stable, raft-kv-rocksdb)	8m 30s
openraft-feature-test (nightly, single-term-leader,serde,singlethreaded)	56s
rt-monoio	47s
examples (nightly, memstore)	58s
examples (nightly, raft-kv-memstore)	2m 18s
stores (stores/memstore)	53s
examples (nightly, raft-kv-memstore-grpc)	1m 49s
tests-feature-test (nightly)	3m 1s
stores (stores/rocksstore)	6m 16s
examples (nightly, raft-kv-memstore-network-v2)	1m 9s
tests-feature-test (nightly, single-term-leader)	2m 59s
examples (nightly, raft-kv-memstore-opendal-snapshot-data)	1m 31s
examples (nightly, raft-kv-memstore-singlethreaded)	1m 12s
examples (nightly, raft-kv-rocksdb)	12m 37s
	1h 21m 3s

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