Lower log message level for nailgun to reduce verbosity #22684

Job	Run time
Classify changes	3s
Ensure PR has a category label	4s
Bootstrap Pants, test Rust (Linux-ARM64)	11m 29s
Bootstrap Pants, test Rust (macOS11-x86_64)	21m 20s
Bootstrap Pants, test and lint Rust (Linux-x86_64)	13m 12s
Build wheels (Linux-ARM64)	0s
Build wheels (Linux-x86_64)	0s
Build wheels (macOS10-15-x86_64)	0s
Ensure PR has release notes	3s
Build wheels (macOS11-ARM64)	0s
Test Python (Linux-ARM64)	3m 10s
Test Python (Linux-x86_64) Shard 1/10	15m 17s
Test Python (Linux-x86_64) Shard 2/10	16m 6s
Test Python (Linux-x86_64) Shard 0/10	16m 23s
Lint Python and Shell	3m 10s
Test Python (Linux-x86_64) Shard 3/10	14m 35s
Test Python (Linux-x86_64) Shard 4/10	24m 22s
Test Python (Linux-x86_64) Shard 5/10	13m 39s
Test Python (Linux-x86_64) Shard 6/10	9m 43s
Test Python (Linux-x86_64) Shard 7/10	14m 31s
Test Python (Linux-x86_64) Shard 8/10	13m 8s
Test Python (Linux-x86_64) Shard 9/10	9m 22s
Test Python (macOS11-x86_64)	12m 44s
Set Merge OK	1s
Merge OK	1s
	3h 32m 23s

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