Lower log message level for nailgun to reduce verbosity #22685

Job	Run time
Classify changes	7s
Ensure PR has a category label	2s
Bootstrap Pants, test Rust (Linux-ARM64)	6m 2s
Bootstrap Pants, test and lint Rust (Linux-x86_64)	10m 15s
Ensure PR has release notes	2s
Bootstrap Pants, test Rust (macOS11-x86_64)	14m 42s
Build wheels (Linux-ARM64)	0s
Build wheels (macOS10-15-x86_64)	0s
Build wheels (macOS11-ARM64)	0s
Build wheels (Linux-x86_64)	0s
Test Python (Linux-ARM64)	3m 20s
Lint Python and Shell	3m 27s
Test Python (Linux-x86_64) Shard 0/10	17m 56s
Test Python (Linux-x86_64) Shard 1/10	16m 53s
Test Python (Linux-x86_64) Shard 2/10	16m 52s
Test Python (Linux-x86_64) Shard 4/10	25m 54s
Test Python (Linux-x86_64) Shard 3/10	15m 14s
Test Python (Linux-x86_64) Shard 5/10	11m 36s
Test Python (Linux-x86_64) Shard 6/10	10m 9s
Test Python (Linux-x86_64) Shard 8/10	13m 48s
Test Python (Linux-x86_64) Shard 7/10	14m 54s
Test Python (Linux-x86_64) Shard 9/10	9m 31s
Test Python (macOS11-x86_64)	12m 6s
Set Merge OK	1s
Merge OK	1s
	3h 22m 52s

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